Journal of Double Star Observations

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1 University Journal of Double of South Star Observations Alabama Journal of Double Star Observations Page VOLUME 7 NUMBER 3 July 1, 2011 Inside this issue: BU 787 AB: An Orbital Binary with Optical Nature Francisco Rica Romero Comparison of the Astrometric Measurements of SHJ355 and STF3022 Obtained with Different Techniques and Software Lorenzo Preti and Giuseppe Micello Study of a new Common Proper Motion Pair at Obsevatorio Kappa Crucis IAU/MPC I26 Alejandro Garro CD Double Star Measures: Jack Jones Memorial Observatory Report #4 James L. Jones Lunar Occultation Observations of Double Stars Report #2 Brian Loader, J. Bradshaw, D. Breit, D. Gault, T. George, D. Herald, E. Iverson, M. Ishida, H. Karasaki, M. Kashiwagura, K. Kenmotsu, D. Lowe, J. Manek, S. Messner, T. Oono, H. Tomioka, H. Watanabe TYC Duplicity Discovery from Asteroidal Occultation by (790) Pretoria Tony George, Brad Timerson,Bill Cooke, Scott Degenhardt, David W. Dunham, Steve Messner, Robert Suggs, Roger Venable, Wayne H. Warren, Jr. HIP Duplicity Discovery from Asteroidal Occultation by (160) Una Tony George, Brad Timerson, Tom Beard, Ted Blank, Ron Dantowitz, Jack Davis, Dennis di Cicco, David W. Dunham, Mike Hill, Aaron Sliski, Red Sumner The Visual Measurements of the Double Star STTA 127 AB Thomas G. Frey, Chandra Alduenda,Rebecca Chamberlain, Chris Estrada, Kristine Fisher, Nathaniel Gilman, Alex Hendrix, Cari Ann Pendergrass A New Video Method to Measure Double Stars Richard L. Nugent, Ernest W. Iverson Astrometric Measurements of the Visual Double Star Epsilon Lyrae Chris Estrada, Sienna Magana, Akash Salam, Abby Van Artsdalen, John Baxter, Mark Brewer, Joseph Carro, Russell Genet, Miranda Graf, Drew Herman

2 Page 137 BU 787 AB: An Orbital Binary with Optical Nature Francisco Rica Romero Astronomical Society of Mérida SPAIN Coordinator of LIADA s Double Star Section ARGENTINA frica0@gmail.com Abstract: BU 787 AB is a double star composed of a bright and blue B9V star of 7.35 magnitude and a white (A0V) secondary of 11.9 magnitude, separated by 5.3. Erceg (1984) calculated orbital parameters for the first time for this double star. In this work, I report several CCD measures performed by some amateurs using telescopes with apertures that range from 0.2 to 0.4 meters. I suspected the possible optical nature of BU 787 AB and decided to perform a detailed astrophysical study of the stellar components and the dynamics of the double star. Several astrophysical tests were applied to determine the nature of BU 787 AB. All of them demonstrated, unambiguously, the optical nature of BU 787 AB. Introduction Nowadays, the works of the amateur are becoming more and more interesting because the difference between the technical levels of what professionals do and what amateurs do is closing. Rica (2008) reviewed some of the important work areas of amateur observers in the double star field. In an orbital calculation work, the author of this article found a binary star listed in the Sixth Catalog of Orbits of Visual Binary Stars (Hartkopf, Mason & Worley 2001) in which the basic astrophysical data looked suspect to him because of the possible optical nature for this binary. The primary is a bright and white star (B9V/A0V) and so its luminosity (absolute magnitude) is bright. The distance modulus would be important and so the primary component would be far away from us. A distant binary with an angular separation of 5.3 in 2007/8 means that the projected separation would likely be a few hundred Astronomical Units (AU) and a large orbital period of thousands of years. But the relative (and linear) motion of B is very large and it is not what I expected for a very large orbital period (lower orbital motion is expected). In this work I comment, in detail, on the astro- Figure 1: BU 787 AB in an image taken March 13, 2008 by Francisco Rica using a LX200R telescope with 0.4 m objective and a focal length of 4117 mm attached to a DMK 41AU02.AS camera. The instrument is located at the Astronomical Observatory of Cantabria (Spain).

3 Page 138 BU 787 AB: An Orbital Binary with Optical Nature physical study for BU 787 AB (=WDS ) to determine the nature of this pair. See Figure 1. The Astrophysical Study A detailed astrophysical study for the stellar components and for the stellar system was performed. The lines of the astrophysical study were published in Benavides et al. (2010) in sections 3 to 10. In the following sections, I complete the report for this study. X-Ray activity The X-ray emission is related to the age of the stars and is inversely proportional to stellar age. While young stars are strong X-ray emitters, old stars are weak X-ray emitters. There are several diagrams that show the relation of X-ray emission with stellar age. X-radiation is absorbed by the Earth's atmosphere, so instruments that detect X-rays must be taken to a high altitude. ROSAT was an X-ray satellite telescope designed by Germany. It was launched in 1990 and operated until The ROSAT All-Sky Survey (RASS) was the first imaging X-ray survey of the entire sky. X-ray digital images show X-ray sources with a very large FWHM of about 2 arcminutes and a calculation of the centroid is difficult, so the AR and DEC for the X-ray source are known with an error of even tens of arc seconds. Optical counterparts for the X-ray sources are not easy to identify, so the astrophysical search for optical counterparts is at an angular distance that ranges from 16 to 40 arcseconds. Photometric data The catalog of the Two Micron All Sky Survey (Cutri et al. 2000; hereafter 2MASS) lists data for the A and B components. While the photometric quality for JHK is good for the primary component, the photometric quality for the secondary is bad and it was not used in this work. Astrometric Measures BU 787 AB is composed of stars with magnitude 7.4 and 11.9 (WDS catalog), separated by more than 5 in the direction of 291 degrees. Since Burnham (1882) discovered its binary nature in 1881, it has had 16 measures which cover an arc of about 60 degrees; and the angular separation increased from 2.0 to 4.5. The measures performed were micrometric, with the use of a refractor or reflector telescope, but the measures were analyzed using the 2MASS CCD image. Some collaborators of the LIADA Double Star Section performed several measures in These new measures are listed in Table 1 in bold font. Our French friend Florent Losse made a measure in using a 0.2 meter telescope with a Barlow 2x lens (total focal length of 4340 mm). The CCD camera used was a CCD Audine with a KAF400 sensor. Florent took 200 images with two different exposure times. Francisco Rica, in March 2008, used a 0.4 meter LX200R telescope located in the Cantabria Astronomical Observatory (north of Spain). For the measures, a CCD ST-8XE was used at the primary focus (focal length of 4115 mm). Ten images of 15 seconds of exposure time were astrometrically reduced using Astrometrica 4.0 to determine the scale and orientation. The scale was of 0.45 per pixel. Ten images of 1 second of exposure time were used to determine θ and ρ using REDUC. Rafael Benavides from Cordoba (South of the Spain) measured this pair on January 16, 2007, using a C11 telescope (0.28 meters) with a focal length of 5420 mm and a pixel scale of 0.41x 0.38 arcseconds. Table 1 lists the historical measures and the LI- ADA measures. This table has the following columns: the epoch of the observations, in column (1); θ (in degrees) and ρ (in arcseconds) values in columns (2) and (3); the number of measures in column (4); the observer code as listed in the WDS catalog, in column (5); last two columns list the residuals O-C with the official orbit. Figure 2 shows a plot of θ versus epoch while Figure 3 shows a plot of ρ versus epoch. The red curves were plotted using the orbital parameters calculated by Erceg (1984) (see Section 4). The Orbital Parameters Erceg (1984) calculated the orbital parameters shown in Table 2. Using the orbital parameters and Hipparcos parallax, a total mass of 2,602M? was obtained! This unrealistic total mass could be caused by terribly wrong orbital parameters or by an erroneous trigonometric parallax. To confirm that the orbital parameters are wrong, I obtained the typical absolute magnitude for Table 2: Orbital parameters for BU 787 AB P = yr To = e = a = " i = 31.40º ω = º Ω = º (Continued on page 140)

4 Page 139 BU 787 AB: An Orbital Binary with Optical Nature Figure 2: The plot shows the theta (θ) values vs the epoch of observations (filled blue points). The red curve was plotted using the orbital parameters calculated by Erceg (1984) Table 1: Observations and Residuals of WDS , BU 787 AB Epoch θ [ o ] ρ["] N Observer Δθ[ o ] Δρ ["] Bu StH Com Hu Bu Doo Bu Fox Gcb Gcb VBs VBs B Hei Pop TMA BVD LOS FMR

5 Page 140 BU 787 AB: An Orbital Binary with Optical Nature Figure 3: The plot shows the rho (ρ) values vs the epoch of observations (filled blue points). The red curve was plotted using the orbital parameters calculated by Erceg (1984). The black line is a linear fit. (Continued from page 138) a B9V (the primary spectral type): about to magnitude. If I correct the V magnitude for the primary by interstellar reddening (Av = +0.35), then a distance of pc is obtained. This corresponds to a parallax of about (in good agreement with the Hipparcos value of ). Using this last value for the parallax, a total mass of 1,716 M? was obtained, so the orbital parameters are unrealistic. Figure 4 shows the orbit calculated by Erceg (1984). The important residuals of the recent measures and the linear trajectory is evident. Astrophysical data The Tycho-2 catalog determined a proper motion of ± 1.5 mas/yr in RA and ± 1.6 mas/yr in DEC. The Hipparcos trigonometric parallax of 3.83 ± 0.72 mas corresponds to a distance of /-40 pc. In the astronomical literature, BU 787 AB has been classified as a B9V star (Jaschek, Conde, & de Sierra (1964), Morgan, Hiltner, & Garrison (1971)) and as a A0V (Kenedy (1983)). In this work a combined spectral type of B9V (in excellent agreement with literature) was obtained using BVIJHK photometry and the combined proper motion. The stellar mass for the primary component is 3.8 solar masses. The spectral type of the secondary is unknown and I assumed a value of 1.0 solar mass. In the literature there are many radial velocity values that range from -13 km/s to +0.7 km/s. Age and Stellar Population In this work a galactocentric velocity of (U,V,W) = (-21, -36, -11) km/s was calculated. According to Eggen s diagrams (1969a, 1969b) BU 787 AB is a member of the young galactic disk. Grenon (1987) defined a kinematic age parameter, fg. A value of 0.21 for fg was obtained in this work corresponding to middle age thin disk stars. Patience et al. (2002) list this double star belonging to the α Persei cluster of about 50 million years. Tables 3 and 4 list the astrophysical parameters for the stellar components and the double star. X-Ray Activity ROSAT PSPC catalog lists an X-ray source near BU 787 AB. Randich et al. (1996) calculated an X-ray luminosity (log Lx) of erg/s. If I consult the diagram of Damiani et al. (1995), the X-ray activity of BU 787 AB is typical of a star with the age of several tens of millions of years. Giampapa, Prosser, and Fleming (1998) studied the X -ray emission of the 70 Myrs open cluster IC This cluster has an X-ray activity similar to BU 787 AB, so it can be said that BU 787 AB has a similar age with IC 4665, that is, about 70 Myrs. BU 787 AB is a member of the α Persei cluster. This cluster has an age of about 50 Myrs, which is in good agreement with the age determined in this work by the X-ray luminosity. Nature of BU 787 AB Using historical measures, a weighted linear fit

6 Page 141 BU 787 AB: An Orbital Binary with Optical Nature Figure 4: The orbit of BU 787 AB calculated by Erceg (1984). The visual micrometric measures are plotted as plus (+). Speckle points are represented as filled blue circles. The lines join the observations with the ephemerid calculated using orbital parameters. North is down and East is right. was performed to calculate a relative motion of B with respect to A of Δx = ± 1.4 mas/yr and Δy = ± 1.4 mas/yr. The baseline of the 19 measures used was years. From the proper motion of A and relative motion of B, I calculated μ(α) = -1.7 ± 2.1 mas/yr and μ(δ) = -1.0 ± 2.2 mas/yr for B. According to the very different proper motions (much greater than 3σ) of B and A, it is likely that B is not gravitationally bound to A, and so it would be an optical companion. But, there exists the possibility that the orbital motion is much greater that the errors in the proper motions. In this case, the proper motion of the components would be incompatible from a mathematical point of view, but the pair of stars could be gravitationally bound by orbiting the center of mass, so I must confirm the nature of BU 787 AB using other tests. I have used several tests (those of Dommanget (1955, 1956), Peter van de Kamp (1961) and Sinachopoulos & Mouzourakis (1992)) that are based on astromechanics. They are described in detail in Benavides et al. (2010). The Dommanget test determined that B would be bound to A if the stellar system is nearer than 30 pc. Hipparcos calculated a trigonometric parallax of 3.83 ± 0.72 mas, corresponding to a distance of /-41 pc. Since the distance for A is 8.7 times greater that the limit of this criterion, it is clear that it is an optical pair. For the criterion of van de Kamp, I need the stellar mass, the projected separation (957 AU), and the annual variation of theta (0.499 deg/yr). This criterion shows that the true critical value for a parabolic orbit is 379 AU 3 yr -2, while the observed projected critical value is of 66,285 AU 3 yr -2, which is much greater than the true value, so B is not bound to A. The tangential velocity corresponding to the observed relative proper motion of B, with respect to A, is 44.6 km s -1. Using the criterion of Sinachopoulos &

7 Page 142 BU 787 AB: An Orbital Binary with Optical Nature Table 3. Astrophysical data for BU 787 AB = WDS Table 4: Data for BU 787 AB = WDS double star Primary Secondary Primary Secondary α 2000 c) 03h 34m 12.95s Reddening, E(B-V) δ 2000 c) +48º 37' 3.1" V 7.35 c) 11.9 a) B V c) ± V I c) ± 0.00 K b) 7.21 ± 0.02 J H b) ± 0.06 H K b) ± 0.06 J K b) ± 0.03 μ(α) [mas/yr] d) ± 1.5 μ(δ) [mas/yr] d) ± 1.6 Spectral Type B9V e) ; A0V f) Trigonometric d) 3.83 ± 0.72 Parallax, π[mas] Reddening, Av V 7.35 a) 11.9 b) B V a) ± V I a) ± 0.00 a) Hipparcos catalog (ESA 1997); b) WDS catalog (Mason, Wycoff & Hartkopf (2003)); V λ = > V tan orb _max The calculated V orb_max is 0.45 AU/yr and λ 21. If I take into account the error in Vtan and I use the expression Vtan 2σ λ = V orb _ max 2 Distance [pc] c) / -41 Mv c) ± 0.41 Reddening, Av g) Radial Velocity +0.7 ± 1.0 h) ; [km/s] a) WDS catalog (Mason, Wycoff & Hartkopf (2003)); b) 2MASS (Cutri et al. 2000); c) Hipparcos (ESA 1997); d) Tycho-2 (Hog et al. 2000) ; e) Jaschek et al. (1964), Morgan, Hiltner, & Garrison (1971); f) Kenedy. (1983), g) Neckel, Th. & Klare (1980); h) Gontcharov (2006). Mouzou, a maximum orbital velocity of 2.1 km s -1 was calculated, so B is not bound to A. Determining the nature using the total mechanical energy In this work I used the total mechanical energy, E, to determine the nature of BU 787 AB. The mathematical process is explained in detail in Brosche, Denis-Karafisan & Sinachopoulos (1992). We cannot calculate the true value of E, but we can calculate a projected value of E (using the relative tangential velocity and the projected separation), called Eo. Eo > 0 is a sufficient condition for a pair being unbound and this condition is fulfilled if then λ' = 9.4 and so BU 787 AB is not gravitationally bound. In summary, the three tests are in agreement with the optical nature of BU 787 AB. So this pair must be flagged with the U code ( Proper motion or other techniques indicate that this pair is nonphysical. ) in the Note column of the WDS Index Catalog. Acknowledgements This research has made use of the Washington Double Star Catalog maintained at the U.S. Naval Observatory and the Astronomical Observatory of Cantabria (CIMA, IFCA-CSIC-UC, AAC). References Benavides, R., Rica, F., Reina, E., Castellanos, J., Naves, R., Lahuerta, L., and Lahuerta, S., 2010, JDSO, 6, 30 Burnham, S. W., 1882, Publ. Washburn Obs. 1. Cutri, R.N., et al., 2000, Explanatory to the 2MASS Second Incremental Data Release, second/index.html.

8 Page 143 BU 787 AB: An Orbital Binary with Optical Nature Damiani, F., Micela, G., Sciortino, S., and Harnden, F. R., Jr., 1995, ApJ, 446, 331. Dommanget J., 1955, "Critère de non-périodicité du mouvement relatif d'un couple stellaire visuel", Observatorio Real de Bélgica, Bull, Astron., t.20, 1955, p. 1. Dommanget J., 1956, "Limites rationnelles d'un catalogue d'etoiles doubles visuelles", Communications de l'observatoire Royal de Belgique, Nº 109, Bull. Astron., t. 20, 1956, p Eggen O.J., 1969a, PASP, 81, 741. Eggen O.J., 1969b, PASP, 81, 553. Erceg, V. 1984, Bull. Obs. Astron. Belgrade #134, 54. ESA SP-1200, ESA Noordwijk, Giampapa, M. S., Prosser, C. F., and Fleming, T. A., 1998, ApJ, 501, 624. Gontcharov, G. A., 2006, AstL, 32, 759. Grenon, M., 1987, JAp&A, 8, 123. Hartkopf, W. I., Mason, B. D., and Worley, C. E., 2001, Sixth Catalog of Orbits of Visual Binary Stars, orb6.html. Hog, E. et al., 2000, AJ, 355, 27. Jaschek, C., Conde, H., and de Sierra, A.C., 1964, PLPla, 28, 1. Mason, B. D., Wycoff, G., and Hartkopf, W. I., 2003, The Washington Double Star Catalog, ad.usno.navy.mil/proj/wds/wds.html. Morgan, W. W., Hiltner, W. A., and Garrison, R. F., 1971, AJ, 76, 242. Patience, J., Ghez, A.M., Reid, I.N., and Matthews, K., 2002, AJ, 123, Neckel, Th. and Klare, G., 1980, A&AS, 42, 251. Randich, S., Schmitt, J. H. M. M., Prosser, C. F., and Stauffer, J. R., 1996, A&A, 305, 785. Rica Romero, F., 2008, RMxAA, 44, 137. Sinachopoulos, D., and Mouzourakis, P., 1992, Complementary Approaches to Double and Multiple Star Research in the IAU Colloquium 135, ASP Conferences Series, Vol. 32. van de Kamp P., 1961, PASP, 73, 389.

9 Page 144 Comparison of the Astrometric Measurements of SHJ355 and STF3022 Obtained with Different Techniques and Software Lorenzo Preti Ferrara - Emilia Romagna, Italy Giuseppe Micello Bologna - Emilia Romagna, Italy luranz@libero.it 7mg8@libero.it Abstract: Astrometric measurements of Sh355 and STF3022 are reported along with standard deviations. Evaluation on the alignment of the images with IRIS 5.59 (by Christian Buil) and comparison between the average data obtained and the data obtained from the image are also discussed. Comparison of results obtained through the use of IRIS 5.59 and REDUC 3.88 (by Florent Losse) is presented. Description of the Stellar Systems Studied and Methods Sh355 (WDS SHJ355: J2000 RA 23h30m01.92s; DEC 58 32'56.1 ) is a nice multiple system in Cassiopeia, whose main component has a blue tint (B3IV). The system has 8 components, where pairs AB and CD are difficult and very unbalanced. Therefore, in this study, we analyzed the system for only the six visual components. F and G, again form a double star (HJ 1887) while component I, belongs to a system attributed to Burnham in 1906 (BU 1149). In the same field of the CCD another system is visible: STF3022 (WDS STF3022: J2000 AR 23h30m52.02s; DEC 58 24'56.5 ). This is actually a triple star. The telescope used was a Newtonian SkyWatcher 200/1000 on a EQ6 SkyScan German equatorial mount. Attached to the telescope was a MAGZERO MZ-5m CCD camera and MPCC Baader Planetarium coma corrector. In Figure 1, you can see the CCD field with the systems SHJ355 and STF3022. Image Capture and Data Analysis Two software packages, IRIS 5.59 and REDUC 3.88, were used to analyze the images to determine the precision and accuracy of both. IRIS 5.59 (by Christian Buil), will perform an astrometric reduction of a CCD field (using GSC- ACT as a reference) and the software implements a useful function to correct optic distortions. The positions of the stars in the GSC-ACT catalog, have a stated accuracy of 0.2" and therefore the goal is to stay in this range. We did an astrometric measurement of 9 stars on 10 images, plus other 9 measurements on the mean image for a total of 99 measurements of coordinates. Table 1 shows the mean of the 10 astrometric measurements. Table 2 shows the measurements taken from the mean image. As can be seen in Figure 2 and from a comparison with Table 1 and Table 2, the mean measurements have minimal differences, compared with direct measurements on the mean image. We have, therefore, an error less than one tenth (Continued on page 146)

10 Page 145 Comparison of the Astrometric Measurements of SHJ355 and STF Table 1: Mean of 10 Astrometric Measurements Using IRIS 5.59 ID RA Dec Sh355 Ab Sh355 Cd Sh355 E Sh355 F Sh355 G Sh355 I STF3022 A STF3022 B STF3022 C 23h 30m s ' h 29m s ' h 30m s ' h 29m s ' h 30m s ' h 29m s ' h 30m s ' h 30m s ' h 30m s '01.41 Figure 1: CCD field with the systems SHJ355 (upper right) and STF3022. Table 2: Measurements on the mean image of the 10 images using IRIS 5.59 ID RA Dec Sh355 Ab 23h 30m s '56.64 Sh355 Cd Sh355 E Sh355 F Sh355 G Sh355 I STF3022 A STF3022 B STF3022 C 23h 29m s ' h 30m s ' h 29m s ' h 30m s ' h 29m s ' h 30m s ' h 30m s ' h 30m s '01.35 Figure 2: Difference Between the Data of Tables 1 and 2.

11 Page 146 Comparison of the Astrometric Measurements of SHJ355 and STF Table 3: Summary data on meaon of 10 measurements with the separation in arc seconds and the relative standard deviations. Rho SH355 CD SH355 E SH355 F SH355 G SH355 I SH355 AB SH355 CD SH355 E SH355 F SH355 G Rho STF3022 B STF3022 C STF3022 A STF3022 B Std. Dev. Rho SH355 CD SH355 E SH355 F SH355 G SH355 I SH355 AB SH355 CD SH355 E SH355 F SH355 G Std. Dev. Rho STF3022 B STF3022 C STF3022 A STF3022 B Table 4: Summary data of the mean of 10 measurements of the postion angle and the relative standard deviations. Theta SH355 CD SH355 E SH355 F SH355 G SH355 I SH355 AB SH355 CD SH355 E SH355 F SH355 G Theta STF3022 B STF3022 C STF3022 A STF3022 B Std. Dev. Theta SH355 CD SH355 E SH355 F SH355 G SH355 I SH355 AB SH355 CD SH355 E SH355 F SH355 G 0.01 Std. Dev. STF3022 B STF3022 C Theta STF3022 A STF3022 B 0.05 of an arc-second. Table 3 shows the summary data of the mean of 10 measurements with the separation in arc-seconds and the relative standard deviations. In Table 4 is the summary data of the mean of 10 measurements of the position angle and the relative standard deviations. Analyzing the data, we found that the standard deviations of Theta, are more or less inversely proportional to Rho. With IRIS, calibration and image orientation are obtained with trigonometry of two distant points of the mean image. The calibration data obtained are Sampling Σ= a.s. / pixel and Orientation Δ=0.211 With REDUC, instead, to make measurements you need to calibrate the image on a pair of stars with known measures to find the orientation and sampling. Tables 5 and 6 show the data obtained with IRIS 5.59 and with REDUC In Figures 3 and 4, one can evaluate the performance of the two software packages. Figure 3 shows the values of position angle: theta values obtained with IRIS are shown in blue and theta values obtained with REDUC are shown in red. Similarly, Figure 4 shows the values of separation in arc-seconds; yellow points are from IRIS and green points from REDUC. From these two graphs, we note that the position angle values are similar. This is not the case for separation where the error increases with the absolute value of the measurement and the relative error, ΔRho / Rho, is around 1% for all data. Comparison with the Official Data of Different Catalogs The data obtained with IRIS and REDUC were compared with the most important catalogs. Table 7 shows the data from the Washington Double Star Catalog, UCAC3 (The third US Naval Observatory CCD Astrograph Catalog, 2009), and PPMXL (Catalog of Positions and Proper Motions on the ICRS, 2010). Analyzing the data in Table 8, we can see that IRIS has a maximum relative error, (Continued on page 149)

12 Page 147 Comparison of the Astrometric Measurements of SHJ355 and STF NAME RA+DEC MAGS PA Table 5: Data Obtained with IRIS 5.59 ST. DEV. PA SEP. ST. DEV. SEP. DATE N NOTES SHJ 355AbCd SHJ 355AbE SHJ 355AbF SHJ 355AbG SHJ 355AbI SHJ 355FG STF3022AB STF3022AC Table 6: Data obtained with REDUC NAME RA+DEC MAGS PA DEV.ST.P A SEP. DEV.ST. SEP. DATE N NOTES SHJ 355AbCd SHJ 355AbE SHJ 355AbF SHJ 355AbG SHJ 355AbI SHJ 355FG STF3022AB STF3022AC Table 7: Data obtained with IRIS and REDUC compared with the most important catalogs. SHJ355 AC SHJ 355 AE SHJ355 FG STF3022 AB STF3022 AC rho theta rho theta rho theta rho theta rho theta WDS UCAC3 (2009) PPMXL (2010) mean IRIS mean REDUC

13 Page 148 Comparison of the Astrometric Measurements of SHJ355 and STF Figure 3: Comparison of the values of theta between IRIS and Reduc. Figure 4: Comparison of the values of rho between IRIS and Reduc.

14 Page 149 Comparison of the Astrometric Measurements of SHJ355 and STF Mean of UCAC3 & PPMXL data Table 8: margin of error expressed as % error. SHJ355 AC SHJ 355 AE SHJ355 FG STF3022 AB STF3022 AC rho theta rho theta rho theta rho theta rho theta e% e% e% e% e% e% e% e% e% e% mean e% WDS Mean IRIS Mean REDUC St. dev. e% (Continued from page 146) while REDUC has the highest average error rate. In both cases the data are certainly consistent with the Washington Double Star Catalog. Conclusions The two different methods software packages yielded values of Theta and Rho that were very similar. The separation (Rho) values had a relative error of 1%, while the position angle (Theta) values had a relative error around 0.2. IRIS and standard astrometric method should be more accurate when the double star is quite large, and a non-linear approximation of the entire star field is needed. For example, a coma corrector can cause distortion of the field, which IRIS can correct, as opposed to REDUC. REDUC, for its simplicity, seems more appropriate for all other cases, when the component stars are close or very close. In these cases IRIS has some difficulty in managing the centroid and the error can be higher. REDUC should be a good choice when using small CCD too, when the field distortion can be ignored. The performance of IRIS can be best with most recent star catalogs (UCAC3 or PPMXL). References IRIS 5.59 by Christian Buil, REDUC 3.88 by Florent Losse, The Cambridge Double Star Atlas by James Mullaney, Wil Tirion Centre de Données astronomiques de Strasbourg: viz-bin/vizier Aladin V.6.0: Washington Double Star Catalog:

15 Page 150 Study of a new Common Proper Motion Pair at Obsevatorio Kappa Crucis IAU/MPC I26 Alejandro Garro Observatorio Kappa Crucis IAU/MPC I26 Córdoba, Argentina Red de Aficionados a la Astronomía garro.alejandro@gmail.com Abstract: In this paper we present the results of a study and observations of 2MASS as components of a common proper motion pair. We calculated and compared proper motions for both stars using catalog images and CCD observations. We used the PPMXL catalog s proper motion data to select this system. This pair, most probably not a binary, needs to be observed and imaged with photometric filters in order to have more reliable data than in current catalogs, except 2MASS (Two Micron All Sky Survey). Halbwachs criterion tells us that this is a CPM system. The criterion of Francisco Rica, which is based on the compatibility of the kinematic function of the equatorial coordinates, indicates that this pair has a probability of 94% to be a physical one [Rica, 2007]. On the other hand, with the absolute visual magnitude of both components, we obtained distance moduli and which put the components of the system at a distance of 2779 and 1282 parsecs. This means, taking into account errors in determining the magnitudes, that the probability that both components are subject to the same distance is 0%, not a binary. We suggest that this pair be included in the CPMDS catalog and the WDS catalog as calibration double star. Introduction Using Aladin Sky Atlas with catalogs and digitized plates of 1979, 1991 and 1992 of an area in the constellation of Pictor, we identified what gives us the impression of being a physical double: 2MASS Table 1 shows the proper motion for the pair given in the PPMXL catalog (a catalog of positions, proper motions, 2MASS, and optical photometry of 900 millions stars). The main purpose is to study this pair to determine if there is a gravitational tie between both components and its nature. Mostly, the material used in this paper was catalog information, and our own plates taken from Kappa Crucis Observatory and its astrometries. The result of this study was achieved by an astrophysical evaluation using kinematic, photometric, spectral and astrometrical data. Table 1: Proper motion of the pair described in this study. Component Proper Motion RA Proper Motion Dec A 45.8 ± ± 3.6 mas/year mas/year B 45.2 mas/year 26.2 mas/year

16 Page 151 Study of a new Common Proper Motion Pair at Obsevatorio Kappa Crucis IAU/MPC I26 Methodology: The methodology used in this work was: Definition of a region on the southern sky delimited by a 4 degrees radius circle. Retrieve all entries in the PPMX catalog in this region. Sort by RA proper motion Review the list identifying 2 stars with almost the same proper motion in RA and Declination. Once a pair is identified visually, retrieve the plates and catalog information with Aladin Sky Atlas. See Figures 1 and 2. Check proper motion of these stars in other catalogs (USNO B1.0, UCAC3, etc.). Retrieve coordinates of both components from many catalogs and observation dates. Retrieve photometry magnitude of both components from 2MASS and other catalogs. Calculate visual magnitude, spectral type and absolute magnitude of both components from the catalog information. Make astrometry measurements of all catalog images and images taken by Kappa Crucis Observatory on January Evaluate a possibly gravitational tie between both components using different criteria such as: Halbwachs, F. Rica Romero, Aitken and Curtiss. Visual Identification After the identification of the binary system candidate, we reviewed its proper motion values from PPMXL catalog, and with Aladin software we retrieved all plates with plate resolution around 1 arcsecond/pixel. Then, we retrieved catalog data of the image field from USNO, UCAC3, PPMX, and 2MASS. Results Unfortunately, photometry data are not reliable, except from the 2MASS project. The visual photometry is clear from the magnitudes B, R and R USNO- B1.0 catalog. With this set of photometry in bands BVRIJHK and using the spectral energy distribution spectra, we obtained F5 III and K0V for the primary and secondary respectively. The photometry is shown in Table 3. Regarding kinematics, the proper motion of the Figure 1: The pair was identified visually and by its proper motion values using Aladin Sky Atlas. Figure 2: Superposition of the data over the catalog image. system obtained from PPMXL is given in Table 1 with the resulting tangential velocity calculation in Table 2. Astrometry from the 2011 measurements is consistent with the catalog data (1986 USNO B1.0 and MASS). See Table 4. Observations from Observatorio Kappa Crucis, January 2011 On 17 January 2011, (Besselian Date: ), we observed this pair from Observatorio Kappa Crucis, Córdoba- Argentina, with a 20 cm. F/5 Newtonian reflector and a Starlight Xpress SXV- H9f CCD camera. With almost a full moon, we imaged seconds exposure time frames. At this time, the pair was almost in the zenith,

17 Page 152 Study of a new Common Proper Motion Pair at Obsevatorio Kappa Crucis IAU/MPC I26 Table 2: Tangential velocity calculation Tangential Velocity Calculation A B mu(alpha) = mu(delta) = Pi (") = Ta (km/s) = Td (km/s) = Vt (km/s)= Table 3: These photometric magnitudes were pulled from 2MASS (infrared) and USNO B1.0 catalogs. Absolute magnitude was calculated using Francisco Rica Romero s astrophysics spreadsheet. Magnitude V Magnitude J Magnitude H Magnitude K Color B - V Color V - I Absolute Magnitude V Bolometric Correction Distance Module Mag R MagB Mag I A B Figure 3: Photo of the pair taken from Observatorio Kappa Crucis. providing the possibility of obtaining the best possible quality images. Having identified the star field to image, we obtained 32 images of 20 seconds of exposure and 30 frames of 30 seconds. Finally we chose the 30 seconds ones, since the companion is more clearly identified and the primary is not overexposed. See Figure 3. Calibration was made with Astrometrica software identifying an effective focal length of mm and camera rotation angle = Astrometrica results are given below: Plate Center Coordinates: RA = 06h 06m 23.70s Dec = ' 58.9" Focal Length = mm Rotation = Pixel Size: 1.33" x 1.33", Field of View: 30.9' x 23.1' Photometry 158 of 195 Reference Stars used: dmag = 0.18mag Zero Point: 26.05mag Table 4: Relative Astrometry Rho (") Theta (º) Component A: Coordinates: ±0.14 ±0.12 ±0.01 Magnitude: 14.0 V Component B: Coordinates: ±0.15 ±0.13 ±0.01

18 Page 153 Study of a new Common Proper Motion Pair at Obsevatorio Kappa Crucis IAU/MPC I26 Magnitude: 15.2 V Next step was relative astrometry with Reduc software using for calibration focal length and camera angle position data obtained with Astrometrica s reduction. Reduc results are given below: Table 5: Reduced Proper Motion BAND Mag(A) H(A) Mag(B) H(B) V K Date : 01/17/2011 Besselian Date: Location : Cordoba, Argentina Conditions : Full Moon Instrument : SXV-H9 CCD Camera Newtonian 20cm F/5 Camera : SXV-H9 (pixels : 6.48 x 6.48) 30 sec. exposure time bin 1x1" / píxel : 0.5 Delta Matrix : (sigma theta : 0.87) Med: (sigma rho : 0.119) Med: deltam=1.69 Effective Focal Length = mm Spectral Type of the Components Using the Francisco Rica Romero s Astrophysics spreadsheet, we can evaluate and calculate the spectral type of each component from photometric data. The result was that the primary component as well its companion are main sequence stars: the primary component is F5V and the companion is K0V. The estimation of the spectral type was made using JHK photometric data from the 2MASS catalog mainly, but to be sure about the nature of each component there is a need to obtain more and more observations with photometric filters. The reduced proper motions for the companions are presented in Table 5. Reduced Proper Motion Diagram (Figure 4) shows that both components are just above the solid separation line and so could be main sequence sub dwarfs (below the line are degenerate sequence stars). Figure 4: Reduced-Proper Diagrams after II. Luyten's White- Dwarf Catalog (Jones, E. M., Astrophysical Journal, vol. 177, p.245). This diagram shows that both components are just above solid line separation and then could be main sequence sub dwarfs Conclusions If we consider reliable the spectroscopy obtained above, we can estimate the sum of the masses to be 2.21 solar masses, at a distance calculated based on the data mentioned above, the criteria of Wilson and Close indicates a physical system. The absolute visual magnitude of both components allow us to calculate the distance moduli: and , which puts us both components of the system at a distance of (primary) and (companion) parsecs, which means that taking into account the errors in determining the magnitudes, we conclude that the probability that both components are at the same distance is more than 52%. Those values are not enouth to say with certainty that this is a binary system, therefore, for now, and until we can obtain more reliable spectral values, we will consider it as a common proper motion system. Was intended to verify the plate kinematics through digitized and are available as 3 images (1979, 1991 and 1992) is not sufficient to establish the proper motions, but because of the relative astrometry between 1979 and 1992 (13 years) could confirm kinematic values outlined above. Astrometry values for 1992 are: θ = 62.7 and ρ = 9.34.'' According to these data, we estimate the parameter (ρ/μ) representing the time it takes the star to travel a distance equal to their angular separation with its motion μ which gives T = 685 years which would give us an interesting likely to be physical. Halbwachs s criterion tells us that this is an MPC system. (An excellent explanation of the Halbwachs'

19 Page 154 Study of a new Common Proper Motion Pair at Obsevatorio Kappa Crucis IAU/MPC I26 criterion can be found in Rica Romero, 2007.) This paper attempts to apply the experience of Rafael Caballero (2009). In summary, with the present information we could not consider this pair as a binary but only as a common proper motion system and there is need to collect more data in the future in order to confirm or discard it as a binary. We suggest that this pair be included in the CPMDS catalog and the WDS as a calibration double star (it could be useful to have more calibration double stars in southern celestial hemisphere). Acknowledgements We want to thank Carlos Krawczenko for his great help on the astrophysical evaluation of this pair, and to Carlos Lasgointy for revising this work. We used Florent Losse s Reduc software for relative astrometry and Herbert Raab s Astrometrica software for astrometry reduction of Observatorio Kappa Crucis s 2011 plates. We used Francisco Rica Romero s Astrophysics spreadsheet with many useful formulas and astrophysical concepts. The data analysis for this paper has been made possible with the use of the SIMBAD astronomical database and VIZIER astronomical catalogs service, both maintained and operated by the Center de Données Astronomiques de Strasbourg ( Roberto Vasconi and Nicolás Vasconi helped in fine tuning of the equipment and the provision of electronic focusers for these observations. References Jones E. M., 1972, Astrophysical Journal, 177, 245. Rica F. 2003, JDSO, 3, 1. Rica F., 2005, JDSO, 1, 8. Rica F., 2006, JDSO, 2, 36. Rica, F., 2007, JDSO, 3, 21. Rica F., 2008, RMxAA, 44, 137. Schlimmer J., 2009, JDSO, 5, 1. Caballero R., 2009, JDSO, 5, 3. Alejandro Garro is a member of Red de Aficionados a la Astronomía (RAA), Córdoba Argentina, and owner of Observatorio Kappa Crucis IAU/MPC (observatory code I26). ( He was the coorganizer of the first and second International Double Stars Workshop 2010 with Edgardo Masa Martín and Florent Losse. He participates in SEDA WDS Austral campaign 2010 and 2011.

20 Page 155 CD Double Star Measures: Jack Jones Memorial Observatory Report #4 James L. Jones Bents Rd NE Aurora, OR Abstract: This paper submits 62 CCD measurements of 53 multiple star systems for inclusion in the WDS. With certain exceptions, observations were made during the calendar year Measurements were obtained using either an SBIG ST-7 CCD camera or an SBIG ST-8 CCD camera and an 11-inch SCT. Introduction Observations and measurements made during the calender year 2006 are reported. Stars observed in years other than 2006 and were also observed in 2006 are included. Thus CHE 3AB includes observations for and Observations were made using a Celestron 11- inch (28 cm) f/10 SCT with a Meade f/6.3 focal reducer/field flattener. This combination yields a pixel scale of approximately 0.95 arcsec/pixel. An SBIG- ST7 camera with a Kodak KAF-401E non antiblooming (NAB) sensor was used for all observations except a single image in That image was taken with an SBIG ST-8 with a Kodak KAF-1603ME NAB sensor. Multiple images of each target were solved using "Astrometrica". Position Angle and Separation and their associated standard deviations were then computed from the RA and Dec of the primary and secondary using a VB Script written by the author. The UCAC-2 catalog was used in most cases for image solution. Where UCAC-2 was unavailable or didn't provide adequate reference stars, USNO-B1.0 was used. The precision of each observation was quantified by calculating the standard deviation of the image set. Results and Discussion Position Angle and Separation measurements are reported in columns PA and SEP respectively in Table 1. The precision of PA and SEP is reported in ERR columns associated with PA and SEP and refers to the standard deviation of PA and SEP for the image set. Column N indicates the number of nights that contributed to the measurement. NAME, RA DEC, and MAGS columns are taken from the WDS CHE 6 (Theta = 194, Rho =12.5, mag 13.11, 14.4) was discovered by P.S. Chevalier in 1907 and was observed a second time in 2004 by access to Digital Sky Survey images utilizing the Aladin applet. (Harshaw, 2004) The WDS Precise Coordinate is listed as It appears that this double consists of Nomad and The coordinate of

21 Page 156 CD Double Star Measures: Jack Jones Memorial Observatory Report #4 NOMAD is SEI 1182 (Theta = 117, Rho = 8.9, mag 9.93, 9.9) was discovered by J. Scheiner in 1895 and was observed a second time in The WDS Precise Coordinate is listed as There is a magnitude 9.8 star located at (NOMAD). However there is no possible companion within 30 arcsec of that star. There is a pair (mag 10.5, 10.8) consisting of NO- MAD and The coordinate of NOMAD is It appears that this is the pair being observed as SEI Acknowledgements This research made use of the Washington Double Star Catalog maintained at the U.S. Naval Observatory and the VizieR catalogue access tool, CDS, Strasbourg, France. References Harshaw, R., 2004, Webb Soc., Double Star Circ. 12, NAME RA DEC MAGS PA ERR SEP ERR DATE N NOTES LDS POU POU HJ CHE 3AB CHE 3AB CHE 3AC CHE CHE CHE Che CHE 17AB CHE 17AB CHE 17AC STF Table continued on next page.

22 Page 157 CD Double Star Measures: Jack Jones Memorial Observatory Report #4 NAME RA DEC MAGS PA ERR SEP ERR DATE N NOTES CHE CHE CHE SEI 7AB SEI 7AC POU POU POU POU POU POU SMA SMA SEI SEI 473AB BKO 109AC SEI HO SEI SEI SEI HJ POU na na POU ELS KZA KZA HJ POU SEI Table continued on next page.

23 Page 158 CD Double Star Measures: Jack Jones Memorial Observatory Report #4 NAME RA DEC MAGS PA ERR SEP ERR DATE N NOTES HJ HJ HJ HJ HLM SEI HJ SEI SEI SEI1188AB SEI1187BC TOB 191BD HJ HJ ES WOR 12AC KU Table Note: 1. Based on 2 images

24 Page 159 Lunar Occultation Observations of Double Stars Report #2 Brian Loader, Darfield, New Zealand (BL) Royal Astronomical Society of New Zealand (RASNZ) International Occultation Timing Association J. Bradshaw, Yugar, Qld, Australia (JB) D. Breit, Morgan Hill, California, USA (DB) D. Gault, Hawkesbury Heights, NSW, Australia (DG) T. George, Umatilla, Oregon, USA (TG) D. Herald, Kambah, Canberra, Australia (DH) E. Iverson, Lufkin, Texas, USA (EI) M. Ishida, Moriyama, Shiga, Japan (MI) H. Karasaki, Nerima, Tokyo, Japan (HK) M. Kashiwagura, Oe, Yamagata, Japan (MK) K. Kenmotsu, Soja, Oakyama, Japan (KK) D. Lowe, Brisbane, Qld, Autsralia (DL) J. Manek, Praha, Czech Republic (JM) S. Messner, Northfield, Minnesota, USA (SM) T. Oono, Kurashiki, Okayama, Japan (TO) H. Tomioka, Hitachi, Ibaraki, Japan (HT) H. Watanabe, Inabe, Mie, Japan (HW) Abstract: Reports are presented of lunar occultations of close double stars observed using video including cases where a determination of the position angle and separation of the pair can be made and other cases where no duplicity has been observed. A number double stars discovered as a result of an occultation are included together with light curves for the event. This paper continues the series of reports of double star measurements made during lunar occultations. The principle and general method of calculation is explained in Herald (2009) and Loader (2010). All occultations used for this paper have been observed using video cameras with either 25 frames (50 fields) per second (Australasia and Europe) or 30 frames (60 fields) per second (USA and Japan). The start and end times of each field of the videos were time stamped to milli-second accuracy. For most events, a light curve of the occultation has been obtained from an analysis of the video of the event, using the Limovie program developed by K. Miyashita. Occultations of double stars result in a stepped light curve, see Herald (2009). The relative size of the step enables an estimate of the magnitude difference of the two stars to be made. Observations are normally made with an unfiltered camera. For each observation an estimate of the slope of the moon s limb at the point of occultation is needed for calculations of the position angle and separation

25 Page 160 Lunar Occultation Observations of Double Stars Report #2 angle of a pair of stars. For this paper use has been made of the Kaguya satellite data. Whilst this gives a more detailed view of the moon s limb than the Watt s corrections, some uncertainty remains. An estimate of these has been built into the uncertainty of the resulting PA and separation. Table 1 continues the series of measures of known double stars for which occultations have been observed from more than one locality. In some cases the occultation observations have been made on different dates, with an interval between them sufficiently short for any change in relative position of the pair of stars to be small. An estimate of the change, derived from WDS data, is given in the notes. Table 2 gives details of similar observations, but of previously unknown double stars discovered as a result of stepped lunar occultations. Two or more observations of the same star enables a determination of the position angle and separation of the pair to be made. In some cases the star had been previously reported as double as a result of a visual observation of an apparently prolonged occultation event. Table 3 presents a further series of discoveries for which only one observation has been made. In this case only a vector separation can be determined along with an estimate of magnitude difference. Only cases where the resulting light curve shows a clearly defined step have been included. Table 4 continues the series of observations of stars which have been reported as possibly double as a result of visual occultation observations, but which subsequently have shown no sign of being double as a result of the observation of occultations using a video system. Only cases with two or more observations with event PAs (the vector angle) separated by at least 10 have been included. The stars in table 4 all have an entry in the Interferometric Catalog. There are 3 possible explanations of the failure to detect a companion star: 1. the vector separation was too small; 2. the magnitude difference is too large for the circumstances of the event; 3. the purported companion does not exist. Names of observers are listed at the head of this paper and are referred to by the two letter code in the table. Light curves, are presented for events involving the discovery of a double star presented in tables 2 or 3. The figures show light curves for lunar occultations of stars. The horizontal axes mostly show the frame number of the video while the vertical axes show the measured light intensity of the star in arbitrary units. In many cases measures have been made of the light intensity in each field of the video recording. WDS refers to the Washington Double Star Catalog and IF to the Interferometric Catalog both published by United States Naval Observatory, Washington. XZ refers to the XZ80 catalog originally published by the USNO. It includes all stars to magnitude 12.5 within 6 40 of the ecliptic, that is all stars which can be occulted by the moon. References Herald, D. SAO97883 a new double star, JDSO, Vol 5, No 4, Loader B. Lunar Occultations of Known Double Stars Report #1, JDSO, Vol 6, No 3, 2010 Table 1: Known double stars: PA and separation measured WDS name XZ RA Dec PA +/- Sep +/- BU Mag. diff BU 536AB Date Observers Note BL DH DB MI 1 SM HK,HW,KK,MI 2 BU HK,HT,TO BOV SM SM 3 STF 499AB HK,KK A1843 AC (CHR 127AB) SM KK,MI,HK 4 BU 225BC DG,DH

26 Page 161 Lunar Occultation Observations of Double Stars Report #2 Table 2: Occultation Discoveries: PA and separation measured Star Name XZ RA Dec PA +/- Sep +/- TYC TYC TYC Mag. diff Date Observers Figure & Note SM Fig. 1 SM HK Fig EI, SM Fig. 3 HD KK, MI Fig. 4 Note 5 HD HK, KK Fig. 5 SAO HK, MI Fig. 6 SAO BL DG Fig. 7 Table 3: Occultation Discoveries: Vector separation only measured Star name XZ RA Dec Vector Angle Vector Sepn. Mag. Diff Date Oberver Figure & Note TYC SM Fig. 8 TYC SM Fig. 9 TYC SM Fig. 10 TYC SM Fig. 11 TYC SM Fig. 12 Note 6 TYC SM Fig. 13 TYC SM Fig. 14 TYC SM Fig. 15 TYC SM Fig. 16 TYC SM Fig. 17 SAO SM Fig. 18 TYC DG Fig. 19 SAO DG Fig. 20 SAO SM Fig. 21 SAO BL Fig. 22 SAO BL Fig. 23 SAO SM Fig. 24 SAO SM Fig. 25

27 Page 162 Lunar Occultation Observations of Double Stars Report #2 Table 4: Companion not observed (possible double star) Star Name XZ RA Dec Vector Angle Resolution Limit Limiting Mag. Diff Date Observer Note BD SM MI DB BD JM MI BD MI HT HD SM HK BD DG SM HD MK HK HD JM DG 7 BD HK DH BD DH DG JB DL BD DG BL HD BL DG DH 8 8 BD DB TG HD BL DH [The Resolution limit is set at no less than two frame intervals [0.080s (PAL) or 0.067s (NTSC)] times the vector rate of motion.] Notes to Tables. 1. Expected change from to : PA -0.74, separation Expected rate of change: PA ca /yr, separation /yr 3. Expected change from to : PA +0.1, separation A1843 AC expected rate of change: PA ca 0.15 /yr, separation nil. There appears to be possible confusion with CHR 127AB. The solution for the PA and separation fits A1843 AC, the observed magnitude difference is closer to CHR 127AB. 5. HD was reported as double as a result of a lunar occultation observation by J Bourgeois, 1988 August 6 and has an entry in the Interferometric Catalog. The star is the primary component of HL TYC is the primary component of POU1110, an 8.8 double. 7. HD = 85 Geminorum. The Interferometric Catalog shows a reported double as a result of an occultation observation by A. Richichi, Observed by DG and DH at a grazing occultation. The resolution limit is nominal.

28 Page 163 Lunar Occultation Observations of Double Stars Report #2 Figure1: Light curves obtained by S. Messner for lunar occultations of XZ Intensity measures were made on each field of the video, that is 60 fields per second. The step for the disappearance lasts for 4 fields, 0.07 second, that for the reappearance lasts for 6 fields, 0.10 seconds. The vertical heights of the steps suggest a magnitude difference of about 0.15 with the fainter star being occulted first. Figure 2: Light curves for occultations of XZ obtained by S. Messner and H. Karasaki. Messner s curve has measures for each field with a step lasting 1.32 seconds. Karasaki s curve has measures for each frame with a step lasting 0.43 second. Figure 3: Light curves for the lunar occultation of XZ obtained by S. Messner and E. Iversen, 2009 February 4. The horizontal axes show the UT time in seconds of the video fields. The position angles of the occultations on the moon s limb were 4 and 69 respectively, resulting in the different step lengths: Messner s step lasts 1.30 seconds, Iversen s 0.14 seconds.

29 Page 164 Lunar Occultation Observations of Double Stars Report #2 Figure 4: Light curves for the occultation reappearance of XZ 4940 obtained by M. Ishida and K. Kenmotsu, 2009 September 10. Measures have been taken each frame, Ishida s step lasting for 0.30 second, Kenmotsu s 0.11 second. Figure 5: Light curves for the occultation of XZ obtained by H. Karasaki and K. Kenmotsu, 2010 March 21. Measures have been taken each frame, Karasaki s step lasting for 0.25 second, Kenmotsu s 0.17 second. There is a noticeable discrepancy in the apparent magnitude differences, 1.6 for Karasaki and 0.7 for Kenmotsu. Figure 6: Light curves for the occultation reappearance of XZ obtained by H. Karasaki and M. Ishida, 2009 November 7. Karasaki s step lasts for 0.47 second, Ishida s 0.43 second.

30 Page 165 Lunar Occultation Observations of Double Stars Report #2 Figure 7: Light curves for occultations of XZ obtained by B. Loader, 2009 July 27 and D. Gault, 2010 June 20. Loader s step lasts 0.17 seconds, Gault s 0.12 seconds, with measures made each frame. Figure 8: Light curve for occultation of XZ obtained by S. Messner, 2007 February 22. The step lasts 0.12 second with measures taken each video field. Figure 9: Light curve for occultation reappearance of XZ obtained by S. Messner, 2009 July 16. The step lasts 1.30 seconds with measures taken each video field. Figure 10: Light curve for occultation reappearance of XZ 5484 obtained by S. Messner, 2006 September 13. The step lasts 0.15 second with measures taken each video field. Figure 11: Light curve for occultation of XZ obtained by S. Messner, 2006 April 4. The step lasts 0.10 second with measures taken each video field.

31 Page 166 Lunar Occultation Observations of Double Stars Report #2 Figure 12: Light curve for occultation of XZ obtained by S. Messner, 2010 February 24. The step lasts 1.89 seconds with measures taken each video field. Figure 13: Light curve for occultation of XZ obtained by S. Messner, 2006 April 5. The step lasts 0.09 second with measures taken each video field. Figure 14: Light curve for occultation of XZ obtained by S. Messner, 2009 April 3. The step lasts 1.98 seconds with measures taken each video field. A second star was visible on the field and was used as a check. Figure 15: Light curve for occultation of XZ obtained by S. Messner, 2007 March 27. The step lasts 0.63 second with measures taken each video field. Figure 16: Light curve for occultation of XZ obtained by S. Messner, 2009 March 7. The step lasts 0.32 second with measures taken each video field. Figure 17: Light curve for occultation of XZ obtained by S. Messner, 2006 May 4. The step lasts 0.34 second with measures taken each video field.

32 Page 167 Lunar Occultation Observations of Double Stars Report #2 Figure 18: Light curve for occultation of XZ obtained by S. Messner, 2006 June 2. The step lasts 0.24 second with measures taken each video field. Figure 19: Light curve for occultation of XZ obtained by D. Gault, 2006 May 6. The step lasts 1.32 seconds with measures taken each video frame. Figure 20: Light curve for occultation of XZ obtained by D. Gault, 2006 June 3. The step lasts 1.88 seconds with measures taken each video frame. Figure 21: Light curve for occultation of XZ obtained by S. Messner, 2006 July 5. The step lasts 0.11 second with measures taken each video field. Figure 22: Light curve for occultation of XZ obtained by B. Loader, 2010 May 2. The step lasts 0.30 second with measures taken each video frame. Figure 23: Light curve for occultation of XZ obtained by B. Loader, 2010 May 4. The step lasts 0.11 second with measures taken each video field.

33 Page 168 Lunar Occultation Observations of Double Stars Report #2 Figure 24: Light curve for occultation of XZ obtained by S. Messner, 2005 October 14. The step lasts 0.14 second with measures taken each video field. Figure 25: Light curve for occultation of XZ obtained by S. Messner, 2009 July 12. The step lasts 0.14 second with measures taken each video field.

34 Page 169 TYC Duplicity Discovery from Asteroidal Occultation by (790) Pretoria Tony George, IOTA Brad Timerson, IOTA North American Coordinator International Occultation Timing Association (IOTA) Bill Cooke, Huntsville, AL Scott Degenhardt, Columbia, TN David W. Dunham, Greenbelt, MD Steve Messner, Northfield, MN Robert Suggs, Chickamauga, GA Roger Venable, Chester, GA Wayne H. Warren, Jr, Greenbelt, MD Abstract: An occultation of TYC by the asteroid 790 Pretoria on 2009 July 19 showed this star to be a double star with a separation of /- 0.4 mas, PA /- 0.2 degrees. Both components of the double star were occulted as seen by all observers. The magnitude of the primary component is estimated to be (VT). The magnitude of the secondary component is estimated to be (VT). Observation On 2009 July 19 seven independent IOTA observers (Cooke, Degenhardt, Dunham, Kazmierczak, Messner, Suggs and Venable) observed the asteroid 790 Pretoria occult the star TYC See the path map in Figure 1. The event was observed from 13 different locations in the USA resulting in 22 separate occultation chords. See Table 1. The target star is magnitude (VT) as listed in the Tycho-2 catalog (VizieR). The asteroid magnitude as predicted by Occult4 was 13.5(v). The expected magnitude drop at occultation was 3.5 magnitudes from the combined magnitude of asteroid and star of 9.97 (VT). The star is not listed in either the Fourth Interferometric Catalog or the Washington Double Star catalog. The light curves obtained from the occultations show two clear events at all but two of the twelve locations where an occultation was observed. There was a clear indication of a double star. At two of the locations, only one occultation was observed. The light curves of the event (which lasted from 7 to 14 seconds) are shown in Figures 2A and Figure 2B. These are not shown in any particular order, but so the reader may see the variety of light curves obtained, and how, in most of them, the double occultation can be seen in the data. Timing of the event disappearance and reappearance was obtained through either: 1. GPS time inserted in each frame, 2. GPS time inserted at the start and end of video and then inserted by frame based on frame count 3. WWV time recording/ simultaneous video recording with frame times interpolated from WWV time tones. A detailed discussion of these timing techniques is given in Nugent [1]. The companion seen in all double-event light curves is nearly equal in brightness to the primary star. Using the Cooke/Suggs light curve data, the (Continued on page 174)

35 Page 170 TYC Duplicity Discovery from Asteroidal Occultation by (790) Pretoria Figure 1: July 19, 2009 (790) Pretoria occultation of TYC Path Mag Table 1: Observer(s), site locations, equipment and methods Site No. Observer Location Telescope Type Tele Diam 1 B. Cooke Huntsville, AL SCT 50 cm 2 S. Degenhardt Lewisburg, TN (mobile) Refractor 5 cm 3 S. Messner Northfield, MN Newtonian 45 cm 4 S. Degenhardt Shelbyville, TN (mobile) Refractor 5 cm 5 R. Suggs Chickamauga, GA SCT 36 cm 6 D. Dunham Silver Point, TN (mobile) Refractor 8 cm 7 R. Venable Five Point, GA (mobile) SCT 10 cm 8 M. Kazmierczak Conyers, GA SCT 20 cm 9 R. Venable 10 R. Venable 11 R. Venable 12 D. Dunham 13 W. Warren Hawkinsville, GA (mobile) Empire, GA (mobile) Chester, GA (mobile) Lawnville, TN (mobile) Crossville, TN (mobile) SCT SCT SCT Refractor SCT 20 cm 28 cm 35 cm 8 cm 13 cm Observing Method Video+GPS time insert Video+GPS other insert Video+GPS time insert Video+GPS other Video+GPS time insert Video+GPS other insert Video+GPS time insert Visual+tape time Video+GPS time insert Video+GPS time insert Video+GPS time insert Video+GPS time insert Video+GPS video Fig 3A and 3B Chord # Result 1 Miss 2 2 nd Star Occ 3,4 2 nd Event only 5,6 Both Occ 8,9 Both Occ 10,11 Both Occ 12,13 Both Occ 14 Wrong Star? 15,16 Both Occ 17,18 Both Occ 19,20 Both Occ 21,22 Both Occ NA Clouded out

36 Page 171 TYC Duplicity Discovery from Asteroidal Occultation by (790) Pretoria Figure 2A: Light curves (various) for visual representation of the data without regard to site order

37 Page 172 TYC Duplicity Discovery from Asteroidal Occultation by (790) Pretoria Figure 2B: Light curves continued (various) for visual representation of the data without regard to site order

38 Page 173 TYC Duplicity Discovery from Asteroidal Occultation by (790) Pretoria Figure 3A: Asteroid profile plot primary and secondary stars aligned Figure 3B: Asteroid profile plot -- primary and secondary stars separate

39 Page 174 TYC Duplicity Discovery from Asteroidal Occultation by (790) Pretoria magnitude drop of the disappearance and reappearance of each star was calculated using the brightness measurements derived by Occular 4.0; the Magnitude calculator routine in Occult4 (Method 3 Magnitudes from light curve values), and the VT combined magnitude from the TYC catalog. The magnitude for each component was determined separately. See Figure 4 for a representative calculation of the primary component. The magnitudes of the two stars are estimated to be (VT) and (VT). The observations were analysed in the standard manner described by Herald [2]. There is no ambiguity in the solution. Assuming the asteroid had an elliptical profile, the double star characteristics are shown in Figures 3A and 3B, and summarized in Table 2. References 1. Chasing The Shadow: The IOTA Occultation Observer s Manual, The Complete Guide to Observing Lunar, Grazing, and Asteroid Occultations, Richard Nugent, April New Double Stars from Asteroidal Occultations, , Dave Herald, Canberra, Australia,, Volume 6 Number 1 January 1, 2010 Table 2: Double star identification and properties Star TYC UCAC Coordinates (J2000*) Mag A Mag B Separation UCAC NOMAD GSC MASS J ±0.1 (VT) ±0.1 (VT) mas ±0.4 mas Position Angle 192.4º ± 0.2º Epoch *Coordinates ICRS (equinox and epoch = J2000.0) as reported in Simbad. Figure 4: Component magnitudes derived from Occult4 magnitude Calculator

40 Page 175 HIP Duplicity Discovery from Asteroidal Occultation by (160) Una Tony George, Umatilla, OR, USA Brad Timerson, IOTA North American Coordinator International Occultation Timing Association (IOTA) Tom Beard, Reno, NV Ted Blank, Hampton, NH Ron Dantowitz, Boston, MA Jack Davis, Dayton, NV Dennis di Cicco, Sudbury, MA David W. Dunham, Greenbelt, MD Mike Hill, Marlboro, MA Aaron Sliski, Boston, MA Red Sumner, Dayton, NV Abstract: An occultation of HIP by the asteroid (160) Una on 2011 January 24 showed this star to be a double star. Both components of the double star were occulted as recorded by three observers. The separation of the two components is ± arcseconds at a position angle of 50.2 ± 12.2 degrees. The magnitude of the primary component is estimated to be 9.2 ± 0.1 V. The magnitude of the secondary component is estimated to be 10.6 ± 0.1 V. Observation On 2011 January 24, nine observers occupying or operating eight sites across the United States observed the asteroid (160) Una occult the star HIP See Figure 1 for the path map of the event. Three sites in Massachusetts observed a two-step drop in brightness, indicating a double star (see Figures 2, 3, 4A and 4B). Three sites had only a primary drop in brightness with no steps visible. For these latter sites, the secondary star may have not been seen due to visual method used or because smaller telescopes or less sensitive video cameras were used resulting in lower signal-to-noise ratio and less ability to see the secondary star (see Figure 5). Two sites had a miss. All recorded occultation times and data from the observers can be found in IOTA records for the event. The observations were made at the sites and with the equipment shown in Table 1. The target star is magnitude 8.93V (Hipparcos - VizieR). The asteroid magnitude as predicted by Occult4 was 12.8(v). The calculated combined magnitude of the star and asteroid is 8.90 V. The expected magnitude drop at occultation was 3.9 magnitudes. The star is not listed in the Fourth Interferometric Catalogue, nor is it listed in the Washington Double Star catalog. Analysis The observations were analysed in the standard manner described by IOTA[1]. Because an inversion model[2] of the asteroid was available, the fit of the double star data within Occult was modified as follows: A. A circular asteroid rather than elliptical was used for the primary star event solution. B. The inversion model was overlaid on the circular solution so it fit the primary star event data (Continued on page 178)

41 Page 176 HIP Duplicity Discovery from Asteroidal Occultation by (160) Una Site No. Observer(s) Location State Telescope Type Brattleboro (mobile) 1 D Dunham Telescope Dia (cm) Method Figure 5 Chords VT Refractor 8 Video+GPS Time Inst 1 Miss Result 2 D di Cicco Sudbury MA SCT 40 Intensified Video+ Video WWV Time Inst 2,3 Two-step 3 M Hill Marlboro MA Refractor 15 Visual+Tape Time Signal 4 Primary 4 R Dantowitz / Clay Center MA Richey- A Sliski Chretien 64 Video+GPS Time Inst 5,6 Two-step 5 T Blank Westborough (mobile) MA SCT 20 Video+GPS Time Inst 7,8 Two-step 6 D Dunham Holyoke (remote) MA Refractor 5 Video+GPS Time Inst 10 Primary 7 T Beard Reno NV Newtonian 14 Video+GPS Time Inst 11 Primary 8 R Sumner / Visual+Tape Time Signal Carson City NV SCT 20 J Davis 12 Miss Figure 1: Occultation Path Figure 2: Di Cicco light curve showing distinct two-step event on D and R

42 Page 177 HIP Duplicity Discovery from Asteroidal Occultation by (160) Una Figure 3: Blank light curve showing at least a distinct step on D Figure 4A: Dantowitz/Sliski light curve showing two-step event on D and R (see expanded Y axis below) Figure 4B: Expanded view of Dantowitz/Sliski light curve showing two-step occultation Figure 5: David Dunham Holyoke, MA light curve showing single step event occultation

43 Page 178 HIP Duplicity Discovery from Asteroidal Occultation by (160) Una Figure 6: Occult4 magnitude calculator using di Cicco light curve data (Continued from page 175) as well as possible. C. All the automatic adjustments for the size, shape and position parameters (except the PA and separation parameters) were turned off so as not to accidentally change those settings D. The secondary star event data was displayed. PA and Separation were adjusted for the secondary star event data until the best fit to the inversion model was obtained. E. All events, primary and secondary star, were displayed to verify the PA and Separation fit. F. the uncertainties for PA and separation were derived by a trial-and-error approach of how much change in PA and separation (separately) could be made before the fit is visually not right. Of the three data sets that recorded the occultation of both stars, the di Cicco data had the most normally distributed brightness data suitable for calculating magnitudes in the step events. Using the di Cicco data, the magnitude drop of the two step disappearance and reappearance was calculated using the brightness measurements derived by Occular 4.0, the Magnitude calculator routine in Occult4 (Method 3 Magnitudes from light curve values) and the combined magnitude from the HIP catalogue (see Figure 6). The magnitudes of the two stars are estimated to be 9.2 V and 10.6 V. The finished plot of the double star fit to the data is shown in Figure 7. Based on the data presented in this report, the double star characteristics are: Star HIP magnitude 8.93 V SAO TYCHO UCAC UCAC NOMAD PPMX Spectral type G5 Coordinates (J2000) Mag A Mag B Sep. P.A (Simbad [3]) 9.2 ± 0.1 V (Estimated from HIP) 10.6 ± 0.1 V (Estimated from HIP) ± arcseconds 50.2± 12.2degrees Acknowledgements The authors would like to acknowledge Scott Degenhardt for his help in analysing David Dunham s video recordings; Dave Herald, Murrumbateman, Australia for his assistance in resolving the correct Position Angle and Separation estimates for this report; and, Josef Durech, Prague, Czech Republic for the creation of the DAMIT inversion model used in the analysis.

44 Page 179 HIP Duplicity Discovery from Asteroidal Occultation by (160) Una Figure 7: Occultation (160) Una occultation of HIP and DAMIT inversion model plot. Note that Chord 1 (a miss) was left off the plot to avoid conflict with other plot text. The direction of travel of the asteroid in the diagram is from upper right to lower left. References 1. New Double Stars from Asteroidal Occultations, , Dave Herald, Canberra, Australia,, Volume 6 Number 1 January 1, Additional tools such as asteroidal light curves (Warner) and asteroidal models derived from inversion techniques (Durech) can be combined with occultation results to yield high resolution profiles. The asteroid light curve inversion method was developed by Kaasalainen and Torppa (2001) and Kaasalainen et al. (2001). It enables one to derive asteroid shape, spin axis direction, and rotation period from its light curves observed over several apparitions. The shape is usually modeled as a convex polyhedron. When the shape model and its spin state are known, its orientation with respect to an observer (sky plane projection) can be computed. Such a predicted silhouette can then be compared with the occultation chords and scaled to give the best fit. See: Durech, J. (2009) Database of Asteroid Models from Inversion Techniques (DAMIT) web site. astro.troja.mff.cuni.cz/projects/asteroids3d. 3. Coordinates ICRS (equinox and epoch = J2000.0) as reported in Simbad.

45 Page 180 The Visual Measurements of the Double Star STTA 127 AB Thomas G. Frey 1, Chandra Alduenda 2, Rebecca Chamberlain 2, Chris Estrada 3, Kristine Fisher 2, Nathaniel Gilman 2, Alex Hendrix 2, Cari Ann Pendergrass 2 1. California Polytechnic State University, San Luis Obispo 2. The Evergreen State College, Olympia, Washington 3. Allan Hancock College, Santa Maria, California Abstract: A team of students, a member of the faculty at The Evergreen State College and two amateur astronomers conducted separation and position angle measurements of the double star STTA 127 AB at the 2010 Oregon Star Party east of Prinville, Oregon. Percent differences between literature and observed values for separation and position angle were less than 1.5%. Field rotation could account for inaccuracy in the position angle due to a long drift time across the astrometric eyepiece. Position angle observations by two teams studying the same star system were carried out allowing the comparisons between altazimuth and equatorially mounted telescopes. Introduction A group of 14 students and their instructor from The Evergreen State College (TESC) in Olympia, Washington, participated in what may be the first scientific research on double stars at the nationally recognized Oregon Star Party (OSP), held from August 11-15, Some of the 14 students had just finished a summer research workshop at Pine Mountain Observatory (PMO) near Bend, Oregon, the previous weekend. All of the students at PMO were new to astrometric research at PMO and were ready to continue their double star observations at the OSP. The students were split into two teams, A and B. Students Fisher, Hendrix, Pendergrass, Gilman, and Alduenda joined their instructor, Chamberlain, along with team leaders Frey and Estrada (Team A, Figure 1) in observing the optical double star, STTA 127 AB, in the constellation Draco. Team B from TESC, lead by Jo Johnson, studied the double star STF The alt-az telescope used for measure- Figure 1: The Evergreen State College team. Front Row: Rebecca Chamberlain, Kristine Fisher, Thomas Frey. Back Row: Alex Hendrix, Cari Ann Pendergrass, Nathaniel Gilman, Chandra Alduenda, Chris Estrada

46 Page 181 The Visual Measurements of the Double Star STTA 127 AB Star Bess. epoch Table 1: Scale Constant Determination. Declin. #Obs AvDrift time(sec) Std dev Mean error Scale constant Dubhe B ments by Team A was an 18 Obsession. The Celestron 12.5 mm illuminated astrometric eyepiece (graciously donated by Celestron to TESC) was calibrated and then separation and position angle measurements were taken. The data was analyzed and each student was assigned a topic to write up for the research paper. Locale The research was carried out at the 2010 Oregon Star Party (OSP), held each summer in the Ochoco National Forest about 35 miles east of Prineville, Oregon. The OSP was founded in 1987 and routinely has astronomers in attendance. The elevation at OSP is about 5000 feet and is located at N and W. The surrounding area is notably high desert so the air is very dry, which resulted in excellent seeing and transparency. This year s OSP was scheduled during the Perseid meteor shower allowing participants an exceptional opportunity to see this event under dark skies. And, since the New Moon appeared on August 10 th, the shower was very impressive. Presentations The OSP routinely has a series of presentations by amateur astronomers during the long weekend. The TESC double star research teams gave introductory presentations to the attendees on the nature of double stars, the history of double star observation, the required instrumentation, and how to measure separation and position angles with an astrometric eyepiece. This was followed by a presentation on data analysis and how to write an astronomical research paper. Following the observations and data reduction, the TESC students individually presented the results of their investigations and gave their personal views of their research experience. Calibration of the Celestron Astrometric Eyepiece The linear scale on the Celestron 12.5 mm astrometric eyepiece, divided into 60 equal divisions, must be calibrated for each telescope-eyepiece assembly to determine the scale constant in arc seconds per division. This has been described at length in other sources (Frey, 2008). The reference star Dubhe in Ursae Majoris was used for this calibration, because its declination lies within the recommended degree range for calibration. The results are given in Table 1. Double Star STTA 127 AB Once the scale constant had been determined, the 18-inch Obsession telescope was two-star aligned and the tracking motors were engaged. Because several of the observers on the team were inexperienced in using the alt-az Newtonian telescope, a wellstudied double star was chosen. The double star selected was STTA 127 AB in the constellation Draco, originally studied in 1844, then having a position angle of 68 degrees and separation of 71.2 arc seconds. The right ascension and declination of the primary star STTA 127 A is 13h 50m 59.4s and m 55.6s, respectively. The most recent study published in the Washington Double Star (WDS) catalog was done in 1999, where the position angle was 63 degrees and the separation was 85.8 arc seconds. The primary and secondary stars had magnitudes of 6.5 and 8.3, respectively. The primary star is a K2IV, a red subgiant and the secondary (SAO 16200) is a G5 Sun-like star. The proper motion vectors, given in milli-arc second per year, for the primary and secondary stars are RA, -176; Dec.,-058 and RA, -095; Dec., +013, respectively (SIMBAD). Such divergent proper motions indicate this is probably an optical double star, although to determine the optical or binary nature of a double star with any certainty, it is important to collect and compile data over many years. Separation Measurements of STTA 127 AB The telescope was two-star aligned and the servo-motors engaged. The Celestron Micro Guide eyepiece was rotated until the central linear scale was parallel with the axis joining the two stars. The distances between the centers of the two stars was estimated to the nearest 0.1 divisions and recorded. Then, using the slow motion controls, the stars were shifted to a new location along the linear scale, a new measurement was made, and the process repeated many times. This method of moving the stars to new locations each time was employed to negate any bias

47 Page 182 The Visual Measurements of the Double Star STTA 127 AB Table 2: Separation Measurements for STTA 127 AB Double star Bess. Epoch Lit. Epoch # Obs. SD/ME Obs. sep Lit. sep % difference STTA 127 AB B / % Table 3: Position Angle Measurements for STTA 127 AB Double star STTA 127 AB Bess. Epoch Lit. Epoch # Obs. SD/ME Obs. PA Lit. PA % difference B / % error that might exist if the stars were continually kept and measured at the same division marks. This also removes systematic errors associated with optical aberrations across the field of view of the system. The results of the separation measurements for STTA 127 AB are shown in Table 2. The SD/ME are the standard deviation and standard error of the mean. The observed and literature separations are given in arc seconds. The percent difference is based on the difference from the most recent literature value. Position Angle Measurements of STTA 127 AB The determination of the position angle using the drift method with an alt-az telescope has been described at length in a previous paper (Frey, 2008). Briefly, it involves disengaging the servo-motors so the telescope becomes a push Dob. The double star is aligned with the linear scale and adjusted manually so when it is released the primary star drifts through the central division (the 30 th division) and continues to drift to the outer protractor scales. There are two potential flaws in this method. First, the primary star of the double star is allowed to drift across the middle 30 division mark on the linear scale. This proper drift alignment is difficult to do and usually takes several attempts to accomplish. Second, a parallax error can occur as the primary star crosses the outer protractor scale that can lead to an erroneous position angle. To circumvent these problems, many drift cycles are carried out and averaged to obtain the best mean measurement. Due to field rotation, the eyepiece was continually adjusted so that the two stars remained aligned with the linear scale. Special effort was made to realign the stars parallel to the scale and the eyepiece was tightened snuggly in the draw tube. The results of the position angle measurements for STTA 127 AB are shown in Table 3. Position angles (PA) are given in degrees. The SD/ME are the standard deviation and standard error of the mean. The percent difference is based on the difference between the observed and the most recent literature values. Cross Comparison of STTA 127 AB and STF 1919 Since the observed position angle for Team A was 2 less than the most recent literature value, Teams A and B agreed to check the data obtained by the opposite team. Team B, lead by Johnson, examined the double star STF 1919 as Team A was observing STTA 127 AB. Team B used a 6 Celestron NextStar Schmidt-Cassegrain on an equatorial mount; Team A was using an 18 Obsession, Newtonian telescope on an alt-az mount. Both teams used the same Celestron 12.5 mm Micro Guide eyepiece. Since we were making observations at the same time and the same site with completely different instruments, a brief comparison of one another s target would be interesting. We only compared the position angles, because the separation values for both teams were in agreement. Table 4 shows the comparison of the data for STTA 127 AB. Team A s initial study with 17 observations was done on August 12, 2010 and was followed up the next night by a shorter second trial run simultaneously with Team B s observation of STTA 127 AB. The average position angle from the 17 and 6 observations taken by Team A are indicated and then

48 Page 183 The Visual Measurements of the Double Star STTA 127 AB Team Double Star Table 4: Teams A&B Compare STTA 127 AB Position Angle # Obs Obs PA degs Lit PA degs SD/ME A 1 st trial STTA 127 AB (61) /0.31 A 2 nd trial STTA 127 AB (62) /0.41 B STTA 127 AB /0.4 Team Double Star rounded to the nearest degree. Table 5 shows the comparison of the data for STF Results For STTA 127 AB, Team B s observed position angle results corresponded exactly with the WDS literature value, where as Team A s values were less than the literature. Since the standard deviation and standard error of the mean statistics for both teams were very close to one another, the difference between the literature and observed position angle for Team A could be due to field rotation. This is a common phenomenon with alt-az mounted telescopes. Argyle (2004) notes The continual changing of the parallactic angle is known as field rotation and it is the main difficulty in measuring double stars with an alt-azimuth mounted telescope. The difficulty lies not so much in the fact that the orientation of the field is continually changing, but in the rate at which it is changing. For alt-azimuth telescopes the rate of field rotation reaches a maximum when the object is at the zenith and at a minimum when the object is on the prime vertical, e.g., when it is due east or due west. A point source like a star at the center of the field appears unchanged over time while the stars toward the edge of the field rotate around the center. When Team A carried out the observation on the second night, the average drift time from the center mark to the outer protractor was 64 seconds. During this drift time, the field of view could have under gone enough field rotation to affect the position angle. Further studies and verification on field rotation involving alt-az telescopes are being performed. The results of these inquiries will be valuable for all Table 5: Teams A&B Compare STF 1919 Position Angle # Obs Obs PA degs Lit PA degs SD/ME B STF /0.1 A STF /0.3 double star investigations with alt-az mounts. These studies will compare the mathematically calculated rotational change with the observed rotation for an alt-az telescope. For STF 1919, the observed position angle for both teams was greater than the literature value. Unlike the 64 second drift time observed by Team A for STTA 127 AB, the drift time for STF 1919 with the Obsession alt-az telescope was only 25 seconds, which is only 0.4 of the longer drift time for STTA 127 AB and less chance for field rotation to occur. Team A s 8 observations were less precise than Team B s results indicated by a standard deviation of twice the amount. Yet the observed position angle of Team A was closer to the literature value. The observations of STF 1919 by teams A and B were done on consecutive nights. Environmental factors such as wind gusts (which were present) could have caused minor differences in measurements, yet not enough to generate outliers. The students expressed satisfaction on completion of the project. They felt more relaxed in doing the research at the OSP after carrying out and completing two projects at PMO. Their motivation and interest was peaked at PMO and they were eager to do further observations at OSP. Their results were additionally impressive because of the six students on the team, only three had made previous measurements and three had never done astrometric measurements prior to OSP. Acknowledgements The team from The Evergreen State College want to express their thanks to Russ Genet and Thomas Smith for reviewing this paper and for their excellent

49 Page 184 The Visual Measurements of the Double Star STTA 127 AB suggestions. Our gratitude is also extended to Dave Powell, Director of the Oregon Star Party 2010, Howard Knytych, Dawn Willard, and all the staff and volunteers at OSP for the invitation to attend and participate in this initial double star research at this event. A special thanks goes to Danyal Medley at Celestron for the donation of a 12.5 mm Micro Guide astrometric eyepiece to Evergreen State College, and to Sarah Pederson (Dean), Theresa Aragon (Dean of TESC Summer School), and Peter Robinson (Director of Lab I and Lab II, and Science Technician at TESC), for purchasing an additional astrometric eyepiece. Our team also wants to recognize Team B s leader, Jo Johnson, and his team, Angel Camama, Nick Brasher, Miles Drake, and Miranda Smith, for their cooperation and assistance with the project. Finally, if it weren t for Russ Genet s initial efforts at contacting officials at OSP, none of this would have taken place. References Argyle, Robert, Observing and Measuring Visual Double Stars, Springer, London, Frey, Thomas G., Spring 2008, Journal of Double Star Observations, 3(2), p Mason, Brian. The Washington Double Star Catalog. July Astrometry Department, U.S. Naval Observatory. wds.html. TheSkyX software: SIMBAD database: Thomas Frey is a Professor Emeritus of Chemistry at California Polytechnic State University. He was a Team Leader at the Pine Mountain Workshop 2009, and the Principle Investigator of the double star group at the Pine Mountain Workshop in Chris Estrada was a Team Leader of a double star group at the Pine Mountain Workshop in Rebecca Chamberlain, is a Member of the Faculty at The Evergreen State College and teaches interdisciplinary programs that link the sciences, humanities, and the arts. She has taught Earth and Sky Sciences for Antioch University's Teacher Education Program, and has worked as the lead Science Interpreter in the Starlab Planetarium at the Pacific Science Center. Chandra Alduenda, Kristine Fisher, Nathaniel Gilman, Alex Hendrix, and Cari Ann Pendergrass are all students at The Evergreen State College.

50 Page 185 A New Video Method to Measure Double Stars Richard L. Nugent International Occultation Timing Association Houston, Texas rnugent@wt.net Ernest W. Iverson International Occultation Timing Association Lufkin, Texas ewiverson@consolidated.net Abstract: A new video method is presented to measure double stars. The double star components are video recorded as they drift across the entire field of view from east to west with the telescope s motor drive turned off. Using the software program LiMovie, specifically written for analysis of occultation videos, (x,y) coordinates are extracted for each star for each video frame. An Excel program written by author RLN analyses the (x,y) positions output by LiMovie for determining position angle (PA), separation and other quantities. The duration of a typical video for an f/10 telescope system ranges between 20 sec 1 minute; this along with a 30 frame/sec recording rate produces 100 s to 1000 s of (x,y) pairs for analysis. The orientation of the video chip and its deviation from the true east-west direction (drift angle) is computed simultaneously along with a scale factor for each video. This provides a calibration for each double star measured. This drift angle and scale factor are used with all (x,y) positions to generate a unique position angle and separation. Typical standard deviations for position angles ranged from 0.3 to 4, and for separations 0.2" to 1.3". A comparison was made using this new method with the Washington Double Star catalog (WDS) entries that had little or no change in PA and separation for years. For these 13 doubles our PA s and separations differed by an average of 0.2 deg and 0.2". Position angles and separations are given for 88 additional stars. Sources of error are discussed along with tips to maximize the quality of the (x,y) data produced by LiMovie. Introduction With the emergence of low cost, higher sensitivity video cameras and digital video recorders (DVR's), video astronomy has reached new levels. This paper describes a new video method to measure separations and position angles of double stars. From a single 20-second to 60-second (or longer) video, this method will analyze thousands of (x,y) positions of the double star components and provide an accurate separation and position angle. The equipment needed to get started is the same as for modern occultation observations: A telescope (equatorial mounted motor driven preferred), an optional Global Positioning Satellite (GPS) time inserter, a video camera and a DVR. In lieu of a DVR, older camcorders can be used for the recordings however any videos acquired must be in AVI (Audio Video Interleave) format for analysis purposes. The principle of this method is as follows: The double star components will drift in the east-west direction from one side of the field of view (FOV) to

51 Page 186 A New Video Method to Measure Double Stars the other side with the telescope s motor drive turned off. The duration of a drift depends on the FOV of the video camera and focal length of the telescope system. No other stars need to be visible on the video except for the double star components. A GPS time inserter will overlay on each video frame the current date and Universal Time (UT) accurate to second. This information is used to identify the start time of the first video frame and the end time of the last video frame of the drift. These times are used to determine scale factors for the video system in arc-seconds/pixel which is crucial for calculating the separation of the components. In lieu of GPS time insertion, the number of video frames in the recording may be used (which will be converted into seconds of time) for each individual drift. This requires that the frame rate per second of the DVR be known precisely. With either of these timing methods, the total drift duration needs to be known to a precision to better than 0.1 second. A freeware program, LiMovie, (Miyashita 2006) written and used for the analysis of occultation videos will output an (x,y) position for each star for each video frame from a 640 x 480 pixel size grid. This (x,y) position output feature from LiMovie was overlooked by it s author Miyashita and the occultation community, yet recognized by one of us (RLN) as a potential new method to measure double stars. At the NTSC (National Television System Committee) video rate of 30 frames per second (fps) of most DVR s, a 25-second video drift will produce 750 (x,y) positions for determining the position angle (θ) and separation (ρ), and a 70-second video drift will produce nearly 2,100 (x,y) positions. LiMovie outputs the (x,y) pairs (with brightness and other data) to a comma separated value (CSV) Excel file. This CSV file is then input into an Excel program written by one of us (RLN) for immediate PA, separation plus statistical results. LiMovie accepts both NTSC and Phase Alternating Line (PAL) format videos. LiMovie will analyze frames at a sec incremental rate for 30 fps NTSC videos and at 0.04 sec increments for 25 fps PAL format videos. GPS time insertion is not mandatory for this method but is preferred for several reasons. Not all DVR s have a 30 fps recording rate so it is crucial to know the start and end times of the drift, which is used for determining the scale factor. With GPS millisecond timing overlaid on each video frame, the frame rate of the DVR can be determined and any dropped frames and other ambiguities associated with a video can be identified. It also simplifies identification of videos for record keeping purposes. The video drift technique presented here is much simpler to utilize than CCD astrometric methods. Only the components of the double star need to be measured for (x,y) position (which is done automatically by LiMovie) as it is not necessary to have any other stars visible. Each video frame will provide a position angle and separation which is later averaged, thus this is not a video stacking method where the user must spend large amounts of time discarding bad frames. Nor is it a CCD astrometry method either, since no RA and DEC positions are calculated for the components. There is no classical least squares CCD image (plate) adjustment performed, thus no star catalog is required either, as no reference star positions are needed. The authors typical drift durations range from 25 seconds with a Meade 14" (35cm) LX-200 to 75 seconds with a 3.5" (9cm) Questar. It is advised that no focal reducers or other optical components be placed between the telescope s objective and video camera as this method is astrometric in nature. Using additional optical components will potentially add unwanted distortions and aberrations. Investigators using this method that wish to resolve close pairs (under 6") may require the use of a barlow lens. The minimum separation we method has resolved is 3.6 arc seconds (see Table 3). The minimum separation that can be resolved is highly dependant on the focal length of the telescope/video system. If the telescope/video camera can discern closer separations, then they should be able to be resolved with the program LiMovie as long as the star images are distinct and not merged. Background noise and atmospheric turbulence becomes an issue when resolving close doubles. Experience shows that the method can handle double star systems that have a maximum 3-4 magnitude difference. A large magnitude difference with a small separation may cause the star images to merge in LiMovie even though they are visually distinct. Very bright stars will have large seeing disks making the centroid determination difficult. The basic rule of thumb in choosing systems to analyze, is that if you can t resolve the components on the video monitor, then they cannot be resolved by the software. Acquisition of Data / Procedure The telescope equipment used is summarized in Table 1. Once setup with telescope, optional GPS time inserter, video camera and DVR, the observer will iden-

52 Page 187 A New Video Method to Measure Double Stars Table 1: Telescopes used in this research. Scale factors will vary slightly due to the declination of the doubles. Focal reducers (f6.3, f3.3) and barlows were sometimes used in acquiring videos. TELESCOPE APERTURE FOCAL LENGTH SCALE FACTOR Meade LX " (35cm) 3550 mm f/10 0.6"/pixel Meade LX-200 8" (20cm) 2000 mm f/10 1.1"/pixel Questar 3.5" (9cm) 1299 mm f "/pixel tify a double star and place it in the video monitor ready for recording. As this is an astrometric method, a steady atmosphere and sharp focus is required to get good results. Investigators should strive to acquire videos when the targets are within 1 hour (15º) of the meridian to minimize the air mass starlight travels through. The goal is to obtain video of the double stars drifting east-west across the entire FOV. The orientation of the top edge of the camera/video chip does not have to be precisely parallel with the east-west line, but should be within 5 degrees (see Figure 2). A few practice drifts will determine if the video camera needs to be rotated. Place the double star system just outside the east edge of the video FOV. Start recording and turn off the telescope motor drive. When the double has drifted outside the opposite (west) side of the FOV, turn off the video recording and turn back on your motor drive. For users with computer controlled telescopes the Appendix offers procedures to turn off the motor drive without losing alignment. The components should be easily resolved on your video monitor, otherwise LiMovie won t be able to resolve them either. If the secondary star does not have sufficient magnitude (brightness), LiMovie may not be able to detect it. LiMovie relies on stars having sufficient brightness levels against the background to be able to extract an (x,y) position. It is always desirable to use the entire video FOV for the drifts to maximize the no. of video frames used for analysis. For investigators using GPS time insertion this requires specific hardware that lies in between the video camera and the DVR. More information on GPS time insertion can found from Nugent (2007) and Nugent (2010). Figure 1 shows a screen shot of LiMovie and it s colored aperture rings wrapped around the double star components. As the stars drift, the (x,y) positions of the centroid of the aperture rings for each frame are stored. For any frame, the date and GPS time can be read off the bottom of the video. LiMovie creates an Excel format CSV file containing the (x,y) data. General instructions for using Li- Movie are found on its website (Miyashita 2006). Nugent (2010) gives specific instructions on how to use LiMovie for this double star method. Analysis of Observations Determining the orientation of the video chip offset from the true east-west direction is needed for each individual video. As shown in Figure 2, the drift angle a is the deviation of the camera chip and telescope orientation vs. the true east-west direction. The drift angle a can be computed in one of two ways. From Figure 2, the triangle ABC is formed from the video chip orientation and the start/stop positions from one component. Using the (x,y) coordinates of these endpoints stored in LiMovie s CSV file, the drift angle a is calculated as follows: α = A triangle is formed for each double star component, hence two drift angles are computed. Averaging these provides the drift angle which will later be used as a correction to the position angle. The second method to determine the drift angle uses a least squares adjustment from the relationship: i arccos AB AC y = mx + b i where y i and x i are the tabular values for either component output by LiMovie into the CSV file. In this case the (x,y) data pairs for all video frames are used in the adjustment. The quantity m is the slope of the line AC, where tan(α) = m and thus α = arctan(m) (3) In the least squares calculation from equation (2), the quantity b is not needed and can be disregarded. Each double star component produces an independent drift angle from equation (2) and these are averaged (1) (2)

53 Page 188 A New Video Method to Measure Double Stars Figure 1. LiMovie screen shot. Colored rings are placed around both double star components by the user. A 3-D contour diagram at right shows the relative intensity of each component and its position on the 50-pixel square window grid. At extreme lower left is the video frame no GPS time is on the bottom of the video and it reads: January 28, h 12min 8.017sec. for a final result. Thus each video provides a unique drift angle. The authors use the least squares method for all drift angle computations. The position angle θ is computed using: xp xs θ = arctan yp y s (4) The primary is determined from the brightness comparison of the two stars. With the primary known, the position angle θ derived will then be corrected for proper quadrant. For each video frame, the separation ρ is computed using the formula: ( ) 2 ( ) 2 ρ = x cos p xs + yp ys δ (5) Figure 2: Drift angle determination. Double stars are green and points A, B and C are the vertices of a right triangle. Drift angle a is defined by BAC. In equations (4) and (5) the quantities x p, x s, y p

54 Page 189 A New Video Method to Measure Double Stars and y s are the (x,y) positions for the primary and secondary star respectively. The declination of either double star is δ. The equation (5) for separation is not rigorous considering we are measuring the projection of a curved celestial sphere onto a flat video chip. However this formula suffices for small separations in double star astronomy. The quantity ρ is formula (5) is in units of pixels. To convert it to arc-seconds multiply by a scale factor. The scale factor is calculated from: scalefactor = ( drifttime) ( x x ) + ( y y ) 2 2 B E B E In equation (6), x B, x E, y B and y E are the beginning and end points of the drift for a component and drifttime is the drift duration in units of seconds. The constant is the sidereal drift rate in arcseconds/second. The drifttime is calculated by knowing the precise start and end time of the drift or the total number of frames of the drift divided by the known frame rate (frames/sec) of the DVR. A scale factor is computed for each double star component and the result is averaged. The units of the scale factor from (6) will be arcseconds/pixel. An Excel program is available that automatically computes the drift angle, scale factor, position angle and separations for all video frames from the output CSV file produced by LiMovie. This Excel program is available upon request from author RLN. The position angles and separations computed are referred to the Epoch and Equator of date. To convert to a catalogued position (such as the Washington Double Star Catalog), the position angle needs to be precessed to the Equator of the catalogued position and then have proper motions applied. Except for stars with the largest proper motions and doubles close to the celestial pole, these corrections can generally be ignored. Results and Discussion Table 2 lists doubles from our data in which the WDS values showed little or no PA and separation movement ( 1 and 0.2") over long periods of time (120+ years). These were chosen to test the validity of this method. Many of these WDS test doubles had zero change in PA and separation over this 120+ year interval. The video drift method s average difference from the WDS values for PA s was 0.2 and for separations was 0.2". If multiple videos were used (N >1 (6) from last Table column) then the values for our PA and separation are weighted averages. As expected, double stars with larger separations have smaller standard deviations for position angle. Scale factors for videos changed slightly for each drift but remained in the range of 1.6"/pixel for the 9-cm (3.5-inch) Questar and 0.6"/pixel for the 35-cm Meade (14-inch) LX-200. Table 3 shows the video drift method results for 88 additional double stars in WDS increasing order. The standard deviations (σ s) of the PA and separations seem larger than those obtained by video stacking and CCD methods. In reality the σ s are a measure of the steadiness of the atmosphere. With a CCD camera that takes, for example, a 10 second exposure, the resultant star images are the sum total of all of the image motions and seeing effects due to the Earth's atmosphere. CCD measuring methods determine the centroid of the central pixel of a single star image. Every second the video drift method computes a new PA and separation based on incremental changes of (x,y) positions due to atmospheric fluctuations and the drift. The final PA and separation are averages of all values for all frames during the drift. With this method no video frames are discarded. For 101 double stars from Table s 2 and 3, Table 4 summarizes the σ s for the video drift method plus comparison summary of PA and separation to the WDS catalog. The following subsections describe sources of error that should be considered when utilizing this technique. Precession and Proper motions To compare results with values from the WDS, one should apply the proper motions of the components and precess your RA, DEC positions to match the date of the published observation. Generally speaking, proper motions are very small and can be neglected and so can precession unless the double star system is close to one of the celestial poles. The vast majority of the entries in the WDS were made in the past 10 years, so precession and proper motions can usually be neglected. Aberrations and distortions of the optical system No optical system is perfect. All telescopes have at least some aberrations and distortions that will affect the position of the optical images. If we were seeking absolute RA, DEC positions of the target compared to a star catalog s reference frame, then we (Continued on page 193)

55 Page 190 A New Video Method to Measure Double Stars Table 2: Comparison of video drift method to the WDS catalog. N is the number of separate video drifts used to obtain the result. If more than 1 video was used for the result (N>1), PA and separation values represent weighted averages from their individual standard deviations. WDS PA σ-pa WDS PA Δ-PA ( ) SEP σ-sep WDS SEP Δ-SEP (") DATE No. video frames AVERAGES N Table 3: Results for 88 double stars using the video drift method. WDS Discoverer magnitudes PA σ-pa Sep" σ-sep date # of video frames N ARG STTA256AB STF STF 10AB STT 10AB HJ H 5 17AB STF 47AB H 5 18AD STF 60AB STF 98AB 7.02, S STF 131AB STT 33AB HJ 1088AB Notes Table 3 continued on next page.

56 Page 191 A New Video Method to Measure Double Stars Table 3 (continued): Results for 88 double stars using the video drift method. WDS Discoverer magnitudes PA σ-pa Sep" σ-sep date # of video frames N STF 163AB STF 180AB H 5 102AB STF 231AB H HJ STF STF 245AB H 6 1AC STTA 27AB PLQ STF STF STF STF STF H 5 117AB STF 366AB STF AG STF 430AB HJ STF STF STF AG STF S STF ENG 19AB SHJ 49AB STF 627AB STF 630A-BC STF 721A-BC STF STF 762AB Notes Table 3 continued on next page.

57 Page 192 A New Video Method to Measure Double Stars WDS Discoverer magnitudes PA σ-pa Sep" σ-sep date # of video frames N STF 872AB STF 900AB STF 924AB S 524AB S 532AC STF STF S S 548AC STF 855AB STT STF1138AB STTA 88AB STF STF1183AB STT H STF1224A-BC STF1245AB S 571AC ENG 38AB STTA 96AB S 583AC STT STF H SHJ HJ STF2280AB STF2379AB SHJ STFA 43AB STF STF STF2998AB H II STF Table 3 Notes: 1. very noisy video yet good result 2. only 8.3sec video clip usable Table 3 (concluded): Results for 88 double stars using the video drift method. Notes

58 Page 193 A New Video Method to Measure Double Stars (Continued from page 189) Table 4: Statistical results from Tables 2 and 3 and a comparison to the WDS catalog. Average std. dev. using video drift method Avg. difference from WDS catalog values Position angle (deg) Separation (arc-second) would have to model for distortions and aberrations since these would affect the actual positions of the stars. However we are only seeking relative quantities here, the separation between the stars and their relative position angle to each other. With the double star components so close to each other any such distortions/aberrations will affect both component images simultaneously and will generally cancel out. Focal reducers/barlows In certain circumstances focal reducers are useful in providing a wider FOV which allows a longer drift time, which provides more (x,y) data pairs to average into the results. A focal reducer increases the apparent brightness of stars to aid in measuring fainter doubles. A barlow lens may be necessary to resolve closer pairs. Focal reducers and barlows have the potential to add distortions and aberrations. Always opt for the least amount of glass between the double stars and your video camera if possible. Gnomonic projection The celestial sphere is curved and the video camera chip is flat. The projection of the curved sky FOV onto the flat video chip normally has a mathematical model to account for this. This is done for CCD astrometry but can be ignored here. The small separations for doubles stars (usually under 2 arc-minutes) can be approximated accurately by a flat (x,y) coordinate system on the surface of your video camera chip. Scale Factor A scale factor is computed for each run. It will be different from one drift run to another due to slight instrument/flexture changes, differential refraction and the declination of the components. The video drift method s results are optimized when the telescope has reached thermal equilibrium and the components are within 1 hour (15 ) of your local meridian. At or near the celestial meridian reduces the amount of air the starlight passes through. Compared to CCD astrometry and other video methods for measuring double stars, the video drift method does not require any dark frames, flat fielding, or any positional information from reference stars from a star catalog. No special cooling or shielding of the video camera is required. There is no longer a need for a separate series of exposures to determine the drift angle orientation from the final measurement image. Investigators simply make a short video, then use the program LiMovie to extract the (x,y) positional information and with a few clicks copy this data into the Excel program for immediate results. The video drift technique presented here has been shown to be a useful independent method for measuring double stars. Acknowledgements The authors would like to thank Kazuhisa Miyashita, LiMovie s author for helpful suggestions in the early part of this research. Mr. Miyashita even wrote a custom version of the program early on. This research has made use of the Washington Double Star Catalog maintained at the U.S. Naval Observatory. Appendix Meade LX-200 users who wish to use this method need not shut down the telescope to stop/start the motor drive. Use these keystrokes: -Setup -Utilities -Telescope -Tracking Rate -Custom -Enter Rate Adj. Under Enter Rate Adj. input -999 to stop the motor drive and then +000 to restart it at the sidereal rate. Another function, Sleep Scope, is a power saving feature and shuts down the Autostar and telescope (but keeps the internal clock running) without forgetting the alignment. Check the LX-200 user manuals for additional details. NexStar users can use this keystroke method to turn the motor drive off and not have to re-align: -NexStar Ready Menu: Tracking Tracking: Mode Mode: Off Press UNDO to return to tracking rates, Alt-Az, EQ North or EQ South.

59 Page 194 A New Video Method to Measure Double Stars References Miyashita, K. 2006, LiMovie, Light Measurement Tool for Occultation Observation Using Video Recorder, limovie_en.html Chasing the Shadow, The IOTA Occultation Observer s Manual, Nugent, R., ISBN , International Occultation Timing Association, 2007, IOTAmanual/Preview.htm Nugent, R., 2010, A New Video Method to Measure Double Stars, Richard/double_stars_video.htm Ernest Iverson is a retired aerospace engineer and avid amateur astronomer. He has been interested in double stars for over 15 years. Richard Nugent holds BS and MS degrees in astronomy from the University of South Florida, and since 1998 is the Executive Secretary of the International Occultation Timing Association.

60 Page 195 Astrometric Measurements of the Visual Double Star Epsilon Lyrae Chris Estrada Cuesta College, San Luis Obispo and Allan Hancock College, Santa Maria Sienna Magana, Akash Salam, Abby Van Artsdalen Arroyo Grande High School, Arroyo Grande, CA John Baxter, Mark Brewer, Joseph Carro, Russell Genet, Miranda Graf, Drew Herman Cuesta College, San Luis Obispo, CA Abstract: Two very different telescopes were used to measure the separation and position angle of the two major components of Epsilon Lyrae, STFA 37 AB,CD. One telescope was a 22 inch non-tracking, alt-azimuth push Dobsonian, while the other was an 8 inch Celestron on an equatorial mount. Both telescopes were equipped with a 12.5 mm Celestron Micro Guide eyepiece, although two different observational techniques were utilized. Separation measurements were within 2% of the mean of recently reported observations by others. The position angles obtained by the equatorial telescope corresponded very well with other recent observations, while the Dobsonian telescope observations departed from these observations by about 3 degrees. We attributed this departure to systematic errors introduced by the Dobsonian position angle observational procedure. We suggest that such systematic errors could be avoided in future alt-az telescope observations by following suggestions made by Thomas Frey. Introduction This research was a portion of the fall 2010 Astronomy Research Seminar held at the Cuesta College South Campus at Arroyo Grande High School in California. The seminar consisted of both Cuesta College and Arroyo Grande High School students (Figure 1) taking this college course in the evening. Two entirely independent separate sets of observations were made and subsequently compared. The first set of observations was made on November 3, 2010, at Star Hill, located near Santa Margarita Lake, California. Estrada brought his Nimbus II 22 inch Dobsonian telescope, which was used by six of us to make these observations. The second set of observations was made by Brewer on November 6, 2010, at Phelan, California, with an 8 inch Celestron Schmidt-Cassegrain telescope. The purpose of the seminar was to introduce students to scientific research. The students were the seminar s decision-makers, establishing with guidance from the instructor what to observe and analyze. The seminar participants decided to make astrometric measurements (separation and position angle) of the wide AB, CD pairs of stars in STFA 37 (Epsilon Lyrae), a double-double. Each of the two very close pairs was treated as a single star, hence we observed the separation and position angle of one close pair with respect to the other. William Herschel, the famous musician turned astronomer, first observed Epsilon Lyrae in He noted in his observing log: A very curious double-

61 Page 196 Astrometric Measurements of the Visual Double Star Epsilon Lyrae Figure 1: The seminar participants clockwise from left front: Akash Salam, Chris Estrada, Joseph Carro, John Baxter, Abby Van Artsdalen, Sienna Magana, Miranda Graf, Drew Herman, and Russ Genet. The telescope is Joseph Carro s Celestron C-11. This college seminar was held in the physics classroom at Arroyo Grande High School. Not present was seminar participant Mark Brewer, who was preparing for observations with an 8- inch telescope. double star. At first sight it appears double at some considerable distance, and by attending a little we see that each of the stars is a very delicate double star. See Figure 2. The first measurements of Epsilon Lyrae were reported by Admiral William Henry Smyth. Smyth was born in Westminster, England, and joined the Royal Navy during the Napoleonic wars where he served in the Mediterranean. In 1817 he met the Italian astronomer Giuseppe Piazzi in Palermo, Sicily. A visit to Piazzi s observatory ignited his curiosity in astronomy and upon his retirement from the Royal Navy he established a private observatory in 1825 in Bedford, England, that he equipped with a 5.9 inch refractor. In 1830 Smyth was the first to record position angle and separation measurements of Epsilon Lyrae. In his 1844 book, Cycle of Celestial Objects, he reported his 1830 observation of Epsilon Lyrae as having a position angle of degrees and a separation of arc seconds. Equipment Our first set of observations was made using the Nimbus II Dobsonian (alt-azimuth) style telescope. This telescope was constructed by Reed and Chris Estrada using methods outlined by Kriege and Berry (1997). Its primary mirror is 22 inches in diameter with an f/4.5 focal length. The mirror was configured by Swayze Optical. The telescope was specifically designed to operate as a manual push Dob, and is Figure 2: Shown above is the type of telescope that Herschel probably used for his double star measurements. If you look at the telescope stand carefully, you'll see two small keys that the observer turns to follow the sky in altitude and azimuth. It probably wasn't a bad system. Herschel made over 200 telescopes with apertures between 6 and 9 inches on alt-azimuth stands similar to the one shown above. He sold them to support himself. The photograph above was taken by Richard Berry of his friend Brian Manning, a very accomplished amateur astronomer, at the Herschel Museum in Bath, England. similar to Herschel s telescope in that it is nontracking. The second set of observations was made using an 8 inch Celestron Schmidt-Cassegrain telescope on an equatorial, clock-driven mount. Celestron Micro Guide astrometric eyepieces were used to make all measurements on both telescopes. The edge illumination of the laser etched reticle was too bright, so a neutral density filter (a wad of tissue paper) was placed in the optical path of the red LED in each eyepiece. Observations Calibration Both teams determined the scale constant on their astrometric eyepiece by observing Epsilon Lyrae itself, timing its drift across the 60 divisions of the linear scale. Eighteen drift times were obtained by the Nimbus II team, but one was discarded because the recorded value was way too small (the recorder noted in the observing log that the stop watch beep came before the observer stop command). The average of the remaining observations was seconds with a standard deviation of 0.33 seconds and a standard error of the mean of 0.08 seconds. We used the Argyle formula (2004) to calculate the scale constant. We found it was 7.40 arc seconds/division with a standard deviation of 0.06 arc seconds/division and a standard error of the mean of 0.02 arc seconds/division.

62 Page 197 Astrometric Measurements of the Visual Double Star Epsilon Lyrae The Celestron 8 team used a scale constant obtained in observations of STFA 43AB. Separation Because Nimbus II is a push Dobsonian telescope without tracking, the stars drifted across the field fairly rapidly. As a result, separations needed to be estimated on the fly. We first attempted to provide left and right scale readings from a central major division, but making two simultaneous estimates was very difficult using this method. Estrada and Genet both suggested that the telescope be initially positioned in such a way that one star would drift through the zero end of the scale. This allowed a single reading to be made of the scale crossing of the second star, while simultaneously only needing to confirm that the first star actually did pass through the zero tick on the end of the scale. Eighteen observations were made by the six observers (Figure 3) and all 18 were used in the analysis. The average separation was found to be 28.6 divisions with a standard deviation of 0.7 divisions and a standard error of the mean of 0.2 divisions. When we applied the scale factor, Z, of 7.40 arc seconds/division to these values we obtained a separation of 211 arc seconds with a standard deviation of 5.0 arc seconds and a standard error of the mean of 1.2 arc seconds. Ten separation measurements were made with the Celestron 8. Since it was a tracking telescope, the measurements did not need to be made on the fly. To reduce any systematic errors, the double star was repositioned on the linear scale between each measurement. The average separation was found to be 28.6 divisions with a standard deviation of 0.7 and a standard error of the mean of 0.2 divisions. When we applied the scale factor to these values we obtained a separation of arc seconds with a standard deviation of 0.4 arc seconds and a standard error of the mean of 0.1 arc seconds. Position Angle Before making the position angle measurements with Nimbus II, the linear scale was aligned to go through the two double stars. The position angle was measured by positioning the telescope such that the primary star drifted through the middle of the linear scale (30 mark), and reading the inner protractor crossing value. Eighteen position angle drifts were obtained with an average inner protractor value of degrees, which translates to an outer protractor value of degrees with a standard deviation of 2.1 degrees and a standard error of the mean of 0.5 degrees. However the outer value of the protractor was not the final value but had to be translated as Figure 3: Observers (left to right) Abby Van Artsdalen, Chris Estrada, John Baxter, Miranda Graf and Sienna Magana all standing in front of the Nimbus II 22 inch Dobsonian telescope. Photo taken by the seminar s instructor, Russ Genet. described by Frey and Frey (2010). The translation yielded a final value of degrees. Position angles were measured in a similar manner with the Celestron 8 telescope except that the eyepiece was rotated 180 degrees between measurements. Also, the outer rather than the inner protractor was used for the measurements. Ten position angle drifts were obtained with an average outer protractor value of degrees with a standard deviation of 0.5 degrees and a standard error of the mean of 0.2 degrees. However the outer value of the protractor was not the final value but had to be translated as described by Frey and Frey (2010). The translation yielded a final value of degrees. Discussion Our observations (rounded to the nearest tenth) are summarized in Table 1, below. Besides our own observations, we included in the last row of the table, the mean, standard deviation, and standard error of the 18 most recent separation and position angles of STFA 37 AB,CD reported in the Washington Double Star Catalog. As can be seen from the table, the separations we found using the two telescopes compared favorably with observations reported in the WDS Catalog one about 2% higher and the other about 2% lower. With respect to position angle, the Celestron 8 was in