Journal of Double Star Observations

Transcription

1 University of South Alabama Journal of Double Star Observations VOLUME 4 NUMBER 2 SPRING 2008 Inside this issue: Ludwig Schupmann Observatory Measures of Large Δm Pairs-Part One James A. Daley 34 Double Star Measurements at the International Amateur Sternwarte (IAS) in Namibia in 2007 Rainer Anton Student Group Measurements of Visual Double Stars Jolyon Johnson, Thomas Frey, Sydney Rhoades, James Carlisle, George Alers, Russell Genet, Zephan Atkins, and Matt Nasser The Relative Proper Motion of HLD 120AB (WDS ) Joerg S. Schlimmer Visual Double Star Measurements with an Alt-Azimuth Telescope Thomas G. Frey 59 Divinus Lux Observatory Bulletin: Report 13 Dave Arnold 66 Measurements of 61 Cygni (STF2758AB, WDS ) Wolfgang Vollmann 74 Observations of Selected Northern Neglected Double Stars Bob Koch 78 Double Star Measurements Using a Webcam: Annual Report of 2007 Joerg S. Schlimmer Observations with a CCD Camera and Various Telescopes Morgan Spangle 84

2 Page 34 Ludwig Schupmann Observatory Measures of Large Δm Pairs-Part One James A. Daley Ludwig Schupmann Observatory New Ipswich NH Abstract: Measurements made at the Ludwig Schupmann Observatory (LSO) in theta and rho space of 107 components in 46 large Δm systems are reported. A comparatively small number of these pairs are physical. For optical components the high proper motion of the mostly nearby primaries can provide extremely accurate relative motions especially for those with a century or more of timely measures. Data for many optical pairs are now plotted in the WDS Catalog of Rectilinear Elements of Visual Double Stars. These elements have been used to hone traditional proper motion values [Mason 2006]. In the case of large Δm systems, the frequency of observation is typically rather low and fresh measures of these challenging systems, both optical and physical, are certainly meaningful. Introduction Difficulties attending CCD measurements of large Δm pairs are described in an article by the author in the Fall 2007 issue of the JDSO [Daley 2007]. The specialized tailpiece optics used to make the measures reported here is also covered in that article. Keen-eyed observers such as W. S. Burnham, Alvan Graham Clark and the Herschel s, William and John, were dominant in the discovery of these contrasting component pairs. They usually employed the biggest reflectors and refractors of the time. It is only recently, with the introduction of the CCD, that amateurs with small telescopes have an opportunity to measure these systems. The Measures The following data is listed in the conventional way. From left to right: the discoverer s designation, WDS identifier (Epoch 2000 RA & Dec), WDS mags rounded off to the first decimal place, (LSO unfiltered CCD magnitudes in bold italics) LSO position angle in degrees, LSO separation in seconds of arc, decimal date of observation, number of nights observed and a notes column. In the notes column entries such as *6m72* signifies 6 previous measures the last being 72 years ago. Other self explanatory items, perhaps of interest, appear in this column. There is no note section as all-in-all the work was routine and without surprise; the optical components, for the most part, showing giant motions and the binaries displaying small but detectable position changes in most cases, the motions being reasonably consistent with previous measures- old and recent. Among the few discoveries are 4 fairly close pairs attendant with systems BAR 1, STF 2579 and AGC 13. The existence (in large numbers) of very faint pairs slowly orbiting bright stars is perhaps fanciful, however, that particular form of stellar architecture certainly interests this writer! Their discovery is probably limited to relatively nearby stars. Contemporary catalog measures of BU 293AD and BU 1192Aa-P gleaned from 2-MASS images were found to be misidentified. The discovery components were easily recovered and measured. Among the high delta m measures, BU 980 AB was the most challenging. Separated by just under 8 arc seconds, it pushed the system capabilities close to its limit. This result encourages the author to try for a solid measure of Sirius, presently at about the same separation but of a greater delta m. Figure 1 shows a CCD image of BU 491 (see measures below) observed under excellent seeing

3 Page 35 Ludwig Schupmann Observatory Measures of Large Δm Pairs-Part One conditions. Only a 6-second exposure was required at full resolution (no binning) to clearly bring out C, the magnitude 15 optical component. The light diagonal bar is the attenuation foil dimming the primary by 10 stellar magnitudes. Note the lack of field stars! This ongoing measurement program is guided by an observation list generated by Brian Mason based on LSO s instrumentation capability and, in general, covers a Δm range of 8 to 12 with the primary component no fainter than 4.5. Measurements are performed with a 9-inch aperture Schupmann medial telescope and an ST-7XE CCD. References B.D. Mason, 2006, "Classical Observations of Visual Binary and Multiple Systems", Proceedings IAU Symposium No Daley, 2007, "A Method of Measuring High Delta m Doubles",, 3, Figure 1: CCD image of BU 491 showing the 15th magnitude C component. The lighter shade diagonal stripe is a result of the attenuation foil. Designation WDS Ident Mags PA Sep Date n Notes H 5 32Aa-B , Alpha And AGC 15AB , m72, Beta Cas BU 491AB , Delta And, binary BU 491AC , m48 BU 1349AB , Alpha Cas BU 1349AC , m100 Table 1: Measures made at the Ludwig Schumann Observatory. Table continued on next page

4 Page 36 Ludwig Schupmann Observatory Measures of Large Δm Pairs-Part One Designation WDS Ident Mags PA Sep Date n Notes H 18AD , BUP 9AB , Zeta And BUP 9AC , binary BUP 9AD , HJ 1057AB , Mu And HJ 1057AC , BAR 1AB , m74, Beta And BAR 1AC , m58 BAR 1AD , m58 BAR 1AE , m128 BAR 1AF , m48 DAL 39AK , DAL 39KL , new pair, mags unfiltered STF 93AC , Polaris STF 93AD , BU 550AB , m45, Aldebaran, binary STFA 2AC , C is an unrelated close STT 545AC , Theta Aur BU 1059A-BC , Mu Gem BU 1059AD , NA LBU 3AE , BU 1192Aa-P , Nu Gem BU 1192Aa-Q , BU 1192Aa-R , BU 1192Aa-S , DAL 33Aa-D , new compnt, mag unfitered STT 77Aa-BC , FOX 150AB , Theta Gem FOX 150AC , DAL 34AD , new compnt, mag unfitered Table continued on next page.

5 Page 37 Ludwig Schupmann Observatory Measures of Large Δm Pairs-Part One Designation WDS Ident Mags PA Sep Date n Notes STF1190AB , Zeta Mon STF1190AC , STF1190AD , m102 BU 1067AC , Omicron UMa HJ 457Aa-B , Delta Cnc, STT 576AC , Delta Leo BU 1282AD , m96, appears to be optical DAL 35AC , new compnt, mag unfiltered POP1219AB-C , Xi UMa BU 604AC , m89, Beta Leo STF1670AB-C , Gamma Vir STF1670AB-D , BUP 150AB , Spica BU 633AB , m73, Gamma Dra BU 633AC , m109 BU 633AD , m92 BU 633AE , m94 BU 633AF , STF2272AU , m61, 70 Oph STF2272AT , m61 STT 342AB , Oph, binary STT 342AC , DAL 36AD , new compnt, mag unfiltered STT 353AB-C , Phi Dra H 5 39AB , Vega STF B 9AC , m126 STF B 9AE , STF3136BC m143 STF 9CD m110 BU 968AB , Zeta Lyr Table continued on next page.

6 Page 38 Ludwig Schupmann Observatory Measures of Large Δm Pairs-Part One Designation WDS Ident Mags PA Sep Date n Notes BU 968AC , m84 HJ 2839AD , m72, 110 Her HJ 2839AE , m72 HJ 2839AB , m72 BU 293AC , Beta Lyr BU 293AD , BU 293AE , BU 293AF , AGC 9AB , Gamma Lyr BU 287AC , Zeta Aql BUP 186AC , Delta Dra BU 653AB , Mu Aql BU 653AC , BU 653BC , J , Iota Aql J 121AB , Alpha Sge J 121AC , STF2579AC , Delta Cyg DAL 37AD , DAL 37DE , new pair, mags unfiltered DAL 37AF , DAL 37FG , new pair, mags unfiltered DAL 27AD , Altair STT 532AB , Beta Aql, binary BU 980AB , m49, Eta Cyg, binary HJ 1455AC , HJ 1455AD , BU 980AE , HJ 1495Aa-B , Cyg HJ 5545AB-C , m46, Beta Del, Table continued on next page.

7 Page 39 Ludwig Schupmann Observatory Measures of Large Δm Pairs-Part One Designation WDS Ident Mags PA Sep Date n Notes STF2704AB-D , STT 594Aa-B , m37, Eps Cyg, BU 676Aa-C , cpm, 2 mags brighter in AGC 13AE , m93, Tau Cyg AGC 13AF , m95 AGC 13AG , cpm DAL 38AE , DAL 38EF , new pair, mags unfiltered BU 1516AB , Zeta Peg HJ 301AB , Xi Peg, neat CCD binary STT 600AB , m99, Lambda And The author, an avid but slowing marathon runner, is retired and observes from his backyard observatory in southern New Hampshire. The main instrument is a 9-inch medial refractor equipped with an ST-7 CCD camera. His recently published book, The Schupmann Telescope, is available from Willmann-Bell,Inc.

8 Page 40 Double Star Measurements at the International Amateur Sternwarte (IAS) in Namibia in 2007 Rainer Anton Altenholz/Kiel, Germany rainer.anton at ki.comcity.de Abstract: A 50cm-Cassegrain and an 11-inch Schmidt Cassegrain at the Internationale Amateursternwarte (IAS) in Namibia was used for observing double and multiple systems at the southern sky. Digital images were recorded with a CCD camera at high frame rates via a firewire interface directly in a computer. Measurements of 55 pairs in 39 systems are presented and compared with literature data. Introduction Usually, seeing limits the resolution of the telescope. However, diffraction limited images of double stars and of other celestial objects - can be obtained by a method, which is sometimes called lucky imaging. By using short exposure times and high frame rates, the moments of good seeing can be frozen and the best images selected for superposition. I have used this technique now for more than ten years with CCDvideo cameras, and found that the error margin in double star positions can be as small as 0.1 arcsec, even with modest amateur telescopes and even under non-optimum seeing conditions [1-3]. The video camera is now replaced by a high-resolution CCD-firewire camera, which delivers a significantly better image quality at relatively high frames rates. In 2002 and 2003, I measured several double star systems in the southern sky. The recent stay in Namibia was also intended to repeat some earlier measurements, which appeared questionable because of significant deviations from older literature data. Equipment and Image Processing The Internationale Amateursternwarte (IAS, is based in Germany and maintains and develops observatories at a guest farm and on the Gamsberg in Namibia, approximately 160 km south-west of Windhuk, the capital of the country. As a member of the IAS, I obtained observing time for one week in May 2007 at a 50cm-Cassegrain and an 11 inch SCT located at the guest farm. At a height of 1880 m above sea level, the seeing conditions were quite good for most of the time, although not optimum. Digital images were recorded with a b/w-ccd firewire camera (DMK21AF04, The Imaging Source) and stored as bitmaps directly in the computer, without conversion into video signals. The chip contains 640x480 square pixels with size 5.6 µm, which results in an image scale of 0.42 arcsec/pix with the C11 (f = 2.8 m), and 0.26 arcsec/pix with the 50 cm Cassegrain (f = 4.5m). These values are about halved when using a Barlow lens. However, the exact calibration of the image scale was obtained by imaging double stars with well known separations. This will be explained in more detail in section III. At short exposure times down to 0.1 msec, I could obtain an image frequency of about 10 to 15 frames per sec with my notebook. This can be somewhat increased, and the amount of data reduced, by limiting the image size to the region of interest. When using a Barlow lens, the high sensitivity of the chip at near infrared wavelengths together with the not sufficient chromatic correction requires insertion of a band filter. This reduces the sensitivity by about 2 magnitudes. As an example, a minimum exposure time of about 0.2 msec is needed for a star of mag 1.0 with the C11, or 0.1 msec with the 50 cm Cassegrain. The actual exposure time is chosen as a compromise between signal-to-noise ratio and pixel

9 Page 41 Double Star Measurements at the International Amateur Sternwarte (IAS) in Namibia in 2007 Figure 1: Three consecutive original frames of g Centauri (with numbers at upper right, exposure time 4 msec, time lapse 80 msec), obtained with the 50cm-Cassegrain with Barlow lens and near-ir filter. The image at lower right is an enlarged view of the superposition of 500 unselected frames (without resampling), corresponding to an exposure time of 2 sec. While there exist some nearly perfect images like no. 670, the superposition produces rather diffuse, overlapping seeing discs. saturation. Generally, a well defined star image should comprise just a couple of pixels. With a set of 4 filters (near infrared, red, green, blue), I also produce composite images of double stars with color contrast. Depending on the seeing, the yield of useful images is typically not more than a few percent. Usually, I choose the best frames by visual inspection and superpose them manually in the computer. While there exist programs for doing this automatically, I encountered difficulties when dealing with image distortions like, for example, unevenly illuminated diffraction rings around the central Airy disc, which can be caused by a slight misalignment of the telescope (coma) combined with seeing effects (see Figure 1). In order to obtain sufficiently well defined images, I choose between 32 and 128 best frames, which are then resampled (often two times), registered and superposed. This results in rather smooth intensity profiles of star images and allows accurate determination of the peak centroid. This is shown in Figure 2 for the system γ (gamma) Centauri and the accompanying line scan of the intensity profile. The image scale was calibrated with two neighboring systems: the relfix

10 Page 42 Double Star Measurements at the International Amateur Sternwarte (IAS) in Namibia in 2007 Figure 2: Left: Superposition of 32 best frames out of 1500 (similar to no. 670 in fig. 1) after two times resampling. The slightly asymmetric diffraction rings may indicate some coma, which however, does not impair the accuracy of determining the peak centroids. Right: intensity profiles in line of the components A-B (blue) and vertically across component B red, dotted). The peak widths at half height of the components are about 0.5 arcsec, the measured separation is 0.47 arcsec with an estimated error margin of +/ arcsec. pair DUN117 in Crux, separation 22.7 arcsec, and alpha Crucis AB, separation 4.0 arcsec, which were imaged under the same conditions. Calibration and Measurements The image scale can in principal be calculated from the pixel and chip dimensions and the focal length of the telescope, as was already mentioned before. However, when using a Barlow lens, the effective focal length depends on its exact distance to the chip. This must be fixed. Therefore, I have done the calibration independently, in the same way as I have described in my earlier papers, namely by measuring a number of systems with well known separations, including but not limited to systems denoted as relatively fixed ( relfix ) in the literature. Only those systems were considered for reference, which exhibit either negligible or well predictable movements based on not too few data. In these cases positions have been extrapolated to the epoch Main sources were the WDS [4], the 4th Catalog of Interferometric Measurements of Binary Stars [5], the 6th Catalog of Orbits of Visual Binary Stars [6], the Sky Catalog [7], and Burnham s Celestial Handbook [8]. All measurements are listed in Table 1 below. Individual remarks are given following the table. Systems included for calibration are marked by shaded lines. The image scale was adjusted such that the average difference between measured and (extrapolated) literature data of these systems became virtually zero. This is also illustrated in Figure 3 below, where the residuals of all measurements are plotted. The resulting image scales (with Barlow) are / arcsec/pixel for the C11, and / arcsec/pixel for the 50 cm Cassegrain. The latter value is based on only two systems, DUN117 and alpha Crucis AB, as was already mentioned in section II, but appears as rather reliable. Discussion and Conclusion It is apparent that diffraction limited images of double stars can almost routinely be obtained by employing the technique of selecting and superposing only the best frames out of longer sequences. In particular, the firewire camera delivers a significantly improved image quality when compared with video. It is remarkable that 28 out of 55 measured separations deviate less than +/- 0.1 arcsec from the corresponding extrapolated literature data. It turns out that among these 28 there are only three relfix systems, but mainly others, which apparently exhibit predictable (Continued on page 51)

11 Page 43 Double Star Measurements at the International Amateur Sternwarte (IAS) in Namibia in 2007 Figure 3: left: Differences Δ rho of measured separations minus extrapolated reference data (residuals) of pairs listed in table 1. Open circles mark binaries, crosses systems denoted as relfix in the literature. Pairs with measured deviations greater than +/- 0.2 arcsec are marked by their numbers. Right: same for the position angles. Pairs with deviations greater than +/- 1 degree are marked by their numbers. Generally, deviations may have various reasons as explained in the notes to table 1. In addition, the error margin for P.A. increases with decreasing separation, due to the limited resolution in the images. Note: For nos. 1 and 2, average values from table 1 are plotted. PAIR RA + DEC MAGS PA meas. rho meas. DATE N D PA D rho NOTES DUN 252AB a* DUN 252AB b DUN 252AC a* DUN 252AC b DON 541AB HJ 4539AB * R DUN 126AB DUN RMK 16AB DUN RHD 1AB CPO Table 1: List of all measurements. Systems used for calibration are marked by shaded lines. Asterisks denote measurements with the 50 cm Cassegrain. System names, positions and magnitudes are taken from the WDS The two columns before the last one show the differences Δ (delta) of measured position angles (PA) and separations (rho) minus reference data (see text). These are also plotted in Figure 3. N is the number of measurements at different nights, with different camera settings and/or filters. Table continued on next page.

12 Page 44 Double Star Measurements at the International Amateur Sternwarte (IAS) in Namibia in 2007 PAIR RA + DEC MAGS PA meas. rho meas. DATE N D PA D rho NOTES HJ CPO DUN 178AC , DUN DUN HJ 4753AB DUN 180AC HJ HDO ARG 28AB ARG 28AC ARG 28AD PZ B 2372AB ? BSO 21AC RMK 21AB RMK 21AC BU 120Aa-B H 5 6Aa-C MTL 2CD DUN MLO 4AB , HJ 4935A-C BSO 13AB HJ 4949AB HJ 4970AB HJ 4970AC BU BU Table 1: List of all measurements. Systems used for calibration are marked by shaded lines. Asterisks denote measurements with the 50 cm Cassegrain. System names, positions and magnitudes are taken from the WDS The two columns before the last one show the differences Δ (delta) of measured position angles (PA) and separations (rho) minus reference data (see text). These are also plotted in Figure 3. N is the number of measurements at different nights, with different camera settings and/or filters.

13 Page 45 Double Star Measurements at the International Amateur Sternwarte (IAS) in Namibia in 2007 H 5 7AB BU 292AC HJ 2822AD HJ 2822AE BU 760AC BU 760AD STN HJ H N S DUN HJ 2866AB HJ 2866AC HJ 2866BC RMK Notes 1a*, 1b: α Cru AB, 1a* measured with 50cm-Cassegrain, 1b with the C11. 2a*, 2b: α Cru AC, 2a* measured with 50cm-Cassegrain, 2b with the C11. The 50cm shows at 100msec a fourth component of about 7.5 mag at 146 o /56.7, a fifth of estimated 12th mag at 167 o /47.4, and a sixth, also very faint, at 227 o /63.9. All these are not listed in the WDS (see fig. 4). 3: α Mus AB. 4 : γ Cen AB, binary, P ~ 85 a, imaged with 50cm-Cassegrain, see fig. 2. 5: β Mus, binary, P = 383a (?), rho deviates from interpolated ephemeris, a similar deviation was already noted in an earlier measurement at : 44.1 o /1.11 [3]. This data seem to follow a trend also seen by other authors. The published orbit may be based on too few measurements. See fig. 5. 6: μ Cru AB, relfix, only few data in the literature, see fig. 6. 7: ξ 2 Cen, common proper motion. 8: θ Mus AB, relfix, few data, see fig. 6. 9: in Centaurus, rho increasing since 1826, few data. 10: α Cen: binary, P ~ 80 a, average data from two measurements on subsequent nights, already measured in 2000 and 2002, all data correspond well to published orbit. See fig : in Lupus, rho virtually fixed. 12: π Lup, already measured in 2002: 66 o /1.7 arcsec. Literature data, including interferometric, show relatively small scatter, see fig : in Lupus, common proper motion, relatively fixed since more than 100 years. 14: in Lupus, optical. The close and faint component B (9.6 mag at 1.2 ) was not detected in the wide

14 Page 46 Double Star Measurements at the International Amateur Sternwarte (IAS) in Namibia in 2007 field image at short exposure times. C fits well to rectilinear elements [9]. 15: κ Lup, common proper motion. Denoted as relfix in Burnham s Celestial Handbook, but PA and rho have noticeably decreased since : ζ Lup, virtually no change since decades, only small scatter of literature data. 17, 18: μ Lup: all common proper motion, confusion in WDS on which is A, which B. See fig : γ Lup, binary, measured position close to published orbit. See fig : ω Lup, only few data in the literature. Already measured in 2002 [3], but recent result appears more reliable due to better image quality. See fig : multiple system in Lupus. AB no significant change since AC reference taken from 1960, as data from 1991 in WDS appear doubtful, rho AC decreased since AD virtually no change since Brightness of C significantly lower than of D in the red band, although listed as about equal (10.40/10.46 mag, respectively) in the WDS. Component C is listed with 11.4 mag in Sky Catalog See fig : ξ Lup, relfix, also measured in 2002: 49 o /10.4. Only small scatter of literature data. 25, 26: in Apus, AB reference last entry in WDS from Own measure possibly inaccurate due to very low brightness of B. AC PA and rho increasing, color contrast yellow-blue. See fig , 28: η Lup, also known as DUN197, relfix, common proper motion. Only few data in the literature with large scatter. Virtually no change of B and C since Already measured in 2002, but recent data appear more reliable due to better image quality. Fourth component with estimated 10 mag at o /135.5 arcsec not listed in WDS. See fig : ν Sco, double double, all common proper motion, AB rho increasing, AC virtually fixed for more than 100 years, CD rho and PA increasing. See fig : in Ara, optical, PA and rho increasing, components exhibit different proper motions, extrapolation of literature data doubtful. Color contrast orange-blue. 33, 34: in Scorpius, also known as BU416, AB binary, already measured in 2002, both positions fit well to published orbit. AC only few data, PA and rho increasing. 35: L7194, in Ara, binary, also measured in 2002, recent measurement appears more accurate. There exist at least two published ephemeris data. Color contrast (G8V/M0V). See fig : in Ara, PA decreasing. 37, 38: in Ara, AB: virtually no change in the last 80 years. AC: PA and rho increasing. A fourth star is at o /52.57 arcsec (9.4 mag), which is plotted in Guide 8.0 [10], but not listed in WDS. A fifth star with estimated 10 mag is at o /13.25 arcsec, which is neither plotted in Guide 8.0 nor listed in WDS. 39: in Sagittarius, relfix, only few data in the literature. 40: in Sagittarius, PA decreasing, rho increasing : μ Sgr, multiple system, rho (AB, AC, AD) have increased since 1830, otherwise only slight changes since decades. Error margins may be increased by overexposure of component A. See fig , 46: η Sgr: already measured in : AC: 321 o /28.2 arcsec, PA increased, rho decreased since 1896; AD: 319 o /92.9 arcsec, PA slightly increased, rho data scattered. Component B (3.6 arcsec from A, 7.8 mag) not detected in the glare of A. See fig : in Sagittarius, PA slowly decreasing. Only few data. 48: in Pavo, only little change since Only few data. 49: HU261, in Sagittarius, binary, measured position very close to published orbit. 50: in Sagittarius, relfix. 51: β Sgr, relfix, common proper motion, few data in the literature.

15 Page 47 Double Star Measurements at the International Amateur Sternwarte (IAS) in Namibia in : in Sagittarius, nice triangle with components of about equal brightness, C probably optical, because of much larger parallax than A and B. See fig. 10. BC very close to rectilinear elements [9]. 55: HJ5177, in Pavo, only few data in the literature. Fits rectilinear elements [9]. Figure 4: Acrux imaged with the 50cm-Cassegrain. Left: without Barlow, 32 frames, 100msec. AB and C are overexposed. Separations AB and AC were measured using the diffraction spikes. Note the faint component at left. Two other even fainter components are marked by vertical lines. In this image, north is up and east is left. Right: AB with Barlow, NIR filter, 32 frames, 2 msec. Figure 5: The binary R207 or β Muscae imaged with the C11, 32 frames, 8.3 msec, Barlow, red filter. This system has also been measured in 2002, and both positions are plotted in the graph at right, adopted from the 6 th Catalog of Orbits of Binary Stars, USNO. It seems that recent measurements by other authors deviate in similar direction from the calculated orbit.

16 Page 48 Double Star Measurements at the International Amateur Sternwarte (IAS) in Namibia in 2007 Figure 6: C11 images of relfix systems μ Crucis (w/o Barlow, 32 frames, 8.3 msec) and θ Muscae (Barlow, red filter, 64 frames, 33 msec). North is down, east is right, as in all following images. Figure 7: Left: Alpha Centauri, C11 image, Barlow, NIR filter, 1 msec. Right: This system was also measured in 2000 and 2002 with a C8-SCT. All three positions are plotted and fit well to the published orbit, adopted from the 6 th Catalog of Orbits of Binary Stars, USNO.

17 Page 49 Double Star Measurements at the International Amateur Sternwarte (IAS) in Namibia in 2007 Figure 8: Double and multiple systems in Lupus. C11 images; π, μ, ω, γ with Barlow, ARG28 and η w/o Barlow, all with red filter. Exposures: π, 32 frames, 20 msec; μ, 64 frames, 48 msec; ω, 32 frames, 0.5 sec; γ, 32 frames, 8.3 msec; ARG28, 250 frames, 0.1 sec; η, 32 frames, 0.1 sec.

18 Page 50 Double Star Measurements at the International Amateur Sternwarte (IAS) in Namibia in 2007 Figure 9: RGB-composites of BSO 21AC in Apus (left) and BSO 13AB in Ara (right). Spectra are classified as G5/? and G8V/MoV, respectively. C11 images. Figure 10: The double-double ν Scorpii (left), and the triple system HJ2866 in Sagittarius. C11 images. See notes. Figure 11: Wide field images of multiple systems μ and η in Sagittarius. C11 images, in both cases 32 frames/0.5 sec w/o Barlow. See notes.

19 Page 51 Double Star Measurements at the International Amateur Sternwarte (IAS) in Namibia in 2007 (Continued from page 42) movements, and even five binaries with well known orbits. On the other hand, there are three relfix systems with larger deviations. Generally, this is caused by too few literature data or too much scatter or both. In this respect, the recent measurements may generally help to improve the statistics of positional data. References [1] Anton, R., 2002, Sky and Telescope, July issue, [2] Anton, R., 2004, The Double Star Observer, 10 (1), [3] Anton, R., 2006,, vol.2 (3), [4] Mason, B.D. et al., The Washington Double Star Catalog (WDS) , U.S. Naval Observatory. [5] Hartkopf, W.I. et al., Fourth Catalog of Interferometric Measurements of Binary Stars, , U.S. Naval Observatory. [6] Hartkopf, W.I. et al., Sixth Catalog of Orbits of Visual Binary Stars, , U.S. Naval Observatory. [7] Sky Catalog , vol. 2, A. Hirschfeld and R. Sinnott, eds., Sky Publishing Corp [8] R. Burnham, Burnham s Celestial Handbook, Dover Publications, New York [9] Hartkopf, W.I. et al., Catalog of Rectilinear Elements of Visual Double Stars, v , U.S. Naval Observatory. [10] The author is a retired physicist from Hamburg University, Germany, and is working on double stars with video techniques since 1995, not only in Namibia, but mostly at home.

20 Page 52 Student Group Measurements of Visual Double Stars Jolyon Johnson 1, Thomas Frey 1, 2, Sydney Rhoades 1, James Carlisle 1, George Alers 1, Russell Genet 1, 2, Zephan Atkins 1, and Matt Nasser 1 1. Cuesta College, San Luis Obispo, CA California Polytechnic State University, San Luis Obispo, CA Abstract: Eight astronomy research seminar participants made visual measurements of double stars as a group project. A reflecting and a refracting telescope were used along with illuminated reticle eyepieces to measure the separation and position angles of known and neglected double stars. The group effort allowed students with a variety of expertise and talent to work together with synergetic effects. What we learned may apply to other group efforts. Introduction and Hypothesis As part of a research seminar at Cuesta College in the fall of 2007, we decided to observe visual double stars. Our expertise ranged from three observers with previous double star observations to two who had made other astronomical observations to three who had never used a telescope for quantitative measurements. Some of us were better at organizing and recording observational data while others were more experienced in writing and editing, so we hypothesized that working together as a group to gather and report on double star observations might have a synergetic effect. The group s goals were to learn how to: 1) work cooperatively; 2) operate the reflecting and refracting telescopes; 3) use the illuminated reticle eyepieces; 4) properly record and process data including statistical calculations; and 5) write and edit a scientific paper. Equipment and Procedures All observations were made at the Coombs Observatory in Atascadero, California. The authors divided into two groups, placing experienced observers in both groups. One group used a C-11 Celestron reflector on an equatorial mount with an illuminated Celestron 12.5mm Micro Guide eyepiece. The other viewed with an Astro-Physics six inch refractor, also on an equatorial mount with an illuminated Meade 12mm Astrometric eyepiece. Observations were made on two nights: September 26 and October 3, To determine the scale factor for each eyepiece, the authors placed a bright star on the eastern-most division of the eyepiece s linear scale. The right ascension motor was then turned off. Using a digital stopwatch, read out to the nearest 0.01 seconds, the authors recorded the time taken for the star to drift from one end of the scale to the other. After finding the average drift time, the authors applied the scale factor equation: t+ cos d z = D Where z is the scale factor in arc seconds per eyepiece division, is the arc seconds per seconds of time that the Earth rotates, t is the average time in seconds for the star to drift across the entire linear scale, d is the declination of the calibration star in degrees, and D is the number of divisions on the scale (60 for the Celestron eyepiece, 50 for the Meade eyepiece). A star with a declination between was chosen to minimize timing errors when using the drift method (Argyle 2004). Separations were determined by centering the primary star and rotating the eyepiece until the linear scale was aligned through the centers of both stars. The observers made multiple measurements of each double star. The number of divisions between the two stars was estimated and recorded to the nearest 0.1 divisions. The resulting average of several trials was multiplied by the scale factor, z, to obtain the separation in arc seconds.

21 Page 53 Student Group Measurements of Visual Double Stars Telescope # of Obs. Average Time (s) St. Dev. Mean Error Scale Const. (as/div) C Astro-Physics Table 1: Average drift times and scale constants for both telescopes Position angles were determined using the drift method. The eyepiece was aligned in the same manner as the determination of the separation, above. The right ascension motor was then turned off to allow the primary star to drift to the protractor around the perimeter of the eyepiece, and its position when crossing the protractor was estimated and recorded to the nearest 0.5. The position angle correction for the Celestron eyepiece was applied (Argyle 2004). This correction was not required for the Meade eyepiece. Multiple trials were recorded and averaged to produce the final position angle. Session One: September 26, 2007 (B ) The first session was devoted to gaining experience in operating the equipment and making calibration and practice observations. None of the authors had used the telescopes at the Coombs Observatory before. It took several trials to become marginally proficient in using the setting circles and slow motion controls to properly position the double stars in the field of view. Frey created a data form for each observer to record: 1) the scale constant drift times; 2) the separations in divisions on the linear scale; and 3) the position angle readings from the circular protractor. The data sheets also contained spaces for the observer to record the date, sky conditions, moon phase, stars to be measured, constellation, and the literature values for separation, position angle, and coordinates. The first session was on a night with a full moon, so both groups observed only well known, bright double stars (with secondary stars brighter than magnitude 9.0). The scale factors for both telescopes were determined using the star Alpha Cephei; magnitude 2.45 and declination The average drift times and derived scale constants of the two telescopes are shown in Table 1. The C-11 group measured the double star Struve 2893 and the Astro-Physics group measured Alpha Cassiopeiae. The apparent magnitudes and coordinates of both well known double stars, according to the Washington Double Star (WDS) Catalog, are shown in Table 2. According to experienced double star observer Dave Arnold, Struve 2893 has a relatively fixed common proper motion while Alpha Cassiopeiae is an optical double. The average observed separations and position angles with standard deviations and standard errors of the mean are shown in Table 3. A comparison of the authors observations with the WDS Catalog separation and position angle of these two double stars is shown in Table 4. The observed separation of the C-11 group differed from the WDS catalog by approximately 0.4 and its position angle differed by 1.5. The observed separation of Alpha Cassiopeiae with the Astro-Physics Star Pri. Mag./ Sec. Mag. Right Ascension Declination Struve /7.9 22h 12.9m m Alpha Cas 2.2/8.8 00h 40.5m m Table 2: Apparent magnitudes and coordinates of the two bright double stars Telescope Star Obs. Sep. St. Dev. Mean Error Obs. PA St. Dev. Mean Error C-11 Struve Astro-Physics Alpha Cas Table 3: Observed separations and position angles with statistical calculations

22 Page 54 Student Group Measurements of Visual Double Stars Telescope Star Separation Position Angle # of Obs. Obs. Sep. Lit. Sep. # of Obs. Obs. PA Lit. PA C-11 Struve Astro-Physics Alpha Cas Table 4: Observed separations and position angles compared with WDS Catalog values of two well known double stars telescope differed by 1.1. All of these differences in measurement were close to the calculated standard error of the mean. However, the position angle of Alpha Cassiopeiae differed by over twenty degrees! This huge difference in position angle may be due to misalignments of the eyepiece because the dim secondary star could not clearly be seen prior to each drift. Session Two: October 3, 2007 (B ) Session two occurred one week after session one during a third-quarter moon. Each group began the session by examining a known, bright double star to check the accuracy and precision of the techniques learned the previous week. The scale constants determined during the previous week were utilized. Table 5 gives the data gathered on the second night for two well known double stars, Beta Cygni (Alberio) and 31 Cygni, along with their corresponding position angles. The observed separation of 31 Cygni is also given. The C-11 group did not measure the separation because they were very confident of their measurements in session one (less than 1% difference from the WDS catalog value). This procedure was performed to be sure proper instrumental techniques were being followed and that observations closely corresponded to recent literature values. The standard deviation and mean error of the observed separation of 31 Cygni are stated as 0.0 arc seconds because the calculated values were far less than the estimated least significant digit (0.1 arc seconds). We attribute the greater precision of these measurements to the brighter magnitude and less difference in the magnitudes of both components as well as wider separations than the previous night s observations. A comparison of observed separation for 31 Cygni and position angle of both double stars to literature values are shown in Table 6. The Astro-Physics group then decided to attempt separation and position angle measurements of 56 Andromedae, a wide double star. The telescope was moved so the setting circles on the refractor were properly positioned for 56 Andromedae and its companion. The literature values for the separation and position angles of 56 Andromedae are 200 and 298, respectively. Observed values were very close to the separation cited in the literature but were significantly different for the position angle. Also the secondary seemed far too dim to be the secondary of 56 Andromedae. However, upon review of TheSky 6 star chart, it was determined that the double star the Astro-Physics group observed was actually adjacent to Telescope Star # of Obs. Obs. Sep. St. Dev. Mean Error # of Obs. Obs. PA St. Dev. Mean Error C-11 Beta Cyg NA NA NA NA Astro-Physics 31 Cyg Table 5: Measurements of two known bright double stars Star Obs. Sep. Lit. Sep. Obs. PA Lit. PA Beta Cygni NA Cygni Table 6: Comparison of observations to literature values for Beta Cygni and 31 Cygni

23 Page 55 Student Group Measurements of Visual Double Stars # of Obs. Obs. Sep. St. Dev. Mean Error Lit. Sep. # of Obs. Obs. PA St. Dev. Mean Error Lit. PA Table 7: Observed separation and position angle of double star BU 1368 BD compared to WDS Catalog values of Andromedae. It was identified in the WDS Catalog as BU 1368 Bb. However, the WDS Catalog now refers to the double star as BU 1368 BD. Table 7 gives the observed data for the double star and compares these with the most recent WDS Catalog values of BU 1368 BD from Conclusions and Recommendations The group of observers found the project to be of significant educational value. Those who had little experience with telescopes learned how to operate them and use them. Others learned the proper methods of recording, analyzing, and reporting observations. All authors learned how to use illuminated reticle micrometers for measuring double stars. During the first session, however, the full moon reduced the contrast between the double stars and the background sky. As a result, the secondary star of Alpha Cassiopeiae, which was significantly dimmer than the primary, was difficult to discern on the linear scale. The linear scale of the Meade Astrometric Eyepiece often covered the position of the secondary, so it is possible that the eyepiece was rotated in such a fashion that only the position of the secondary was revealed and thus the secondary was not properly oriented to get a proper position angle reading. Also, working with unfamiliar equipment proved challenging. Members of both groups had trouble adjusting and reading the setting circles used to position the target double stars. Manipulation of the slow motion controls to position the double stars on the scale was also difficult because there was considerable backlash. For future observations involving first time observers, we suggest that the owner or an experienced operator of the telescopes align the double stars and allow the students to estimate the separation and follow the drift patterns for measuring scale constants and position angles. We recommend preparing star charts of the field of view in advance. A reviewer of this paper, Bob Buchheim, suggested that with amateur equipment (whose polar alignment and setting circles are likely to be less than perfect), the use of a star chart of the field of view is absolutely required in order to be sure of the identification of the stars. One does not want to spend the whole evening gathering data on a star system and then find out the next morning that it was the wrong one! The overall experience of double star measurements by the research group was enlightening. Our hypothesis was confirmed since we learned, through a synergetic effect, a great deal about double stars themselves and the techniques required to quantify the parameters that describe them. We hope what we learned about group measurements will encourage others to observe double stars in similar educational settings. Acknowledgments We thank Lee Coombs for providing instructions on the operation of his telescopes and for the use of his observatory. We also thank Dave Arnold for his review and analysis of the observed double stars. Finally, we thank Vera Wallen, Robert Buchheim, and Tom Smith for their helpful reviews of this paper. The Washington Double Star Catalog was used throughout the project. References Argyle, Robert. Observing and Measuring Visual Double Stars. London: Springer, Mason, Brian. The Washington Double Star Catalog. May, Astrometry Department, U.S. Naval Observatory. Jolyon Johnson, Sydney Rhoades, James Carlisle, George Alers, Zephan Atkins, and Matt Nasser were enrolled in the physics research seminar at Cuesta College. Thomas Frey, also enrolled in the physics research seminar, is a Professor Emeritus of Chemistry at California Polytechnic State University. Russell Genet is a Professor of Astronomy and led the research seminar at Cuesta College. He is also a Research Scholar in Residence at California Polytechnic State University and Director of the Orion Observatory,

24 Page 56 The Relative Proper Motion of HLD 120AB (WDS ) Joerg S. Schlimmer Seeheim-Jugenheim, Germany Abstract: Using two new measurements made in 2007, I present a new relative proper motion, a rectilinear path, and ephemeris for the double star HLD 120AB. Description HLD 120 is a double star in the constellation Bootes. Its structure was discovered in 1882 by Edward Singleton Holden. Both components have a brightness of 8.3 and 9.9 magnitude. Since its discovery in 1882 it was only observed 7 times. The last observation was done in This is the reason to list it as neglected double star. HLD 120 has a proper motion of -046 mas/year in declination and -062 mas/ year in right ascension. Table 1 shows the seven measurements of HLD 120 listed in the Washington Double Star Catalog (Mason 2007). About my measurements My double star measurements were made with an 8-inch Newtonian telescope with a focal length of 1500 mm. To record the observations, a standard webcam is used. This webcam has a small CCD chip with square pixel of 5.6 x 5.6 micrometers. The resolution is 640 x 480 pixels. The reproduction scale of the optical system is about arc seconds / pixel. The faintest magnitude of stars which can be recorded is about For analyses of the webcam records I use the REDUC software package, written by Florent Losse. For double stars with components of equal brightness, the typical standard deviation of my optical system is about 0.25 arc seconds. In cases of high contrast differences between the components or low signal to noise ratio of faint components, the standard deviation is about 0.5 arc seconds. Anyway, reproduction tests show mostly better results (Schlimmer 2007). I observed HLD 120AB in The best 60 frames of my record were analyzed. I got a separation of a.s. ± 0.47 a.s. and a position angle of ± 2.0 Date PA Separation Mag A Mag B Rev. Code Aperture Hld Com Bu_ Fox Doo Abt Cll Table 1: Past measurements of HLD 120.

25 Page 57 The Relative Proper Motion of HLD 120AB (WDS ) a.s. ± 0.05 a.s. and a position angle of ± Evaluation of the measurements Figure 1 show all measurements of HLD 120AB from WDS and also the new measurements, labeled Schlimmer2007 and Buchheim2007. Maverick points are in red. For plotting, the measurements were transformed from polar to Cartesian coordinates by following formula: x = d sin(pa) y = d cos(pa) Figure 1: Plot of the measurements of HLD 120AB, labeled Schlimmer2007 and Buchheim2007, along with past measurements. Maverick points are in red. Further Measurements of HLD 120AB in 2007 A further measurement was done by Robert K. Buchheim at Altimira Observatory in (Buchheim, 2008). He observed HLD 120AB nearly at the same time that I did. He reported a separation of were d is the distance or separation in arc seconds and PA is the position angle. Linear Fit and Residuals For the best measurements (without both mavericks), a linear fit and residuals were calculated. The residuals are a good control for the quality of the measurements. Following are the mathematical equation and results from the linear fit: y = mx + b m = b = Figure 2 shows the linear fit to the measurements Results Cartesian coordinates for closest approach: linear fit residuals Linear fit residuals rev. code pa distance for distance for distance for pa for pa Hld not used not used not used not used Com Bu_ Fox Doo Abt Cll not used not used not used not used Schlimmer Buchheim Table 2: Comparison of measured values to linear fit

26 Page 58 The Relative Proper Motion of HLD 120AB (WDS ) ρ = ± 0.2 φ = ± 0.5 μ x = ± 0.72 mas/yr μ y = ± 0.04 mas/yr μ = ± 0.43 mas/yr T0 = ± 1.74 years Ephemeris Because of the small value of the proper motion, it is a long time to the point of closest approach in year Table 3 shows predicted future PA s and separations for HLD 120. References Schlimmer, Joerg, 2007,, 3, Figure 2: Linear fit to measurements of HLD 120AB. x0 = y0 = The Washington Double Star Catalog, Brian D. Mason, Gary L. Wycoff, and William I. Hartkopf, 2007, Buchheim, Robert K., 2008, Journal of Double Star Observations, 4, Time for closest approach: T0 = years Polar coordinates for closest approach: Proper motion: ρ = φ = μ x = mas/yr μ y = mas/yr μ = mas/yr Calculation of Errors Because of the new measurements made independently by Schlimmer und Buchheim, the current position of HLD 120AB is well determined. For calculation of errors the differences between the results of Schlimmer and Buchheim divided by 2 was taken. year ρ (as) φ (deg) Table 3: Predicted future separation and position angle for HLD 120AB

27 Page 59 Visual Double Star Measurements with an Alt-Azimuth Telescope Thomas G. Frey California Polytechnic State University San Luis Obispo, CA Abstract: An alt-az mounted Newtonian telescope was used to determine the separation and position angle of seven known and five neglected double stars. The problem of field rotation was solved by modifying the usual observing technique. Separation and position angle determinations are described, and the standard deviations and mean errors for these measurements are presented. The direction of future studies is outlined. Introduction Professional astronomers have carried out visual double star measurements for over 200 years. These scientists measured the separation between double stars in arc seconds, and the position angle in degrees that defined the orientation of pairs with respect to celestial north. Over time, the orbital motion of each star can create a change in the observed separation and position angle if the pair proves to be binary in nature. A binary star revolves around a common center of mass. Today s amateur astronomers continue to evaluate these changes with fairly simple equipment. The usual recommended setup includes an equatorial mounted telescope with tracking motors, a laseretched astrometric eyepiece, and a stopwatch. This study, however, utilizes an altitude-azimuth (alt-az) mounted telescope instead of an equatorial mounted telescope. Alt-az mounts are seldom used in double star measurements due to the rotation observed in the field of view. This motion can affect both the accuracy and precision of the measurement of the position angle. Yet, with minor adjustments made at regular intervals during the observing session, both separation and position angle measurements made on known double stars correlate closely to literature values. Once it was determined that the measuring techniques were accurate and precise, additional measurements on neglected double stars listed in the Washington Double Star Catalogue were made. Double Star Observation: Equatorial vs. Alt-Az Mounts Most observers involved in double star measurements, including Argyle (p.x) and Teague (p.112), recommend the use of equatorial mounted telescopes. Such telescopes have drive motors that are oriented so the right ascension axis rotates around the north celestial pole, canceling out the Earth s rotation and the image in the eyepiece remains stationary. The equatorial telescope can be equipped with an illuminated reticle eyepiece such as the 12.5 mm Celestron Micro Guide or the 12 mm Meade astrometric eyepiece. Both eyepieces have similar configurations: a linear scale in the middle and a 360 protractor scale around the circumference of the field of the eyepiece. The linear scales are divided into 60 and 50 equal divisions on the Celestron and Meade eyepieces, respectively. Sometimes an external protractor scale is mounted to the base of the eyepiece to more accurately measure the position angles, as described by Tanguay (p.116) and Johnson and Genet (p.147). Separation between double stars is determined by using the slow motion control of the equatorial telescope to align the pair on the linear scale. Then esti-

28 Page 60 Visual Double Star Measurements with an Alt-Azimuth Telescope mate the number of divisions on the scale between the centers of the stars to the nearest tenth. The number of arc seconds represented by each scale division is previously determined by using either the drift method with a star of known celestial coordinates, or calibration double stars alone, that have had no change in separation in 50 years. Position angles are measured again by using a slow motion control, this time to move the primary star to the center of the linear scale. The eyepiece is rotated until the secondary star is also on the linear scale. The drive motors are turned off and the pair drifts across the field of view until the primary reaches the protractor scale at the outer edge of the field. The drive motors are re-engaged and the position angle is indicated by the position of the primary star on the protractor scale. The axis of a telescope attached to an alt-az mount rotates about the zenith, not the celestial pole like an equatorial mount. Even if the alt-az telescope is equipped with drive motors, stars in the field of view rotate around objects in the center of the field. The closer a celestial object is to the zenith, the faster the rotation in the field. This rotation makes any type of imaging (astrophotography or CCD imaging) problematic. It also can affect double star measurements, especially position angle determination. Field rotation can be compensated for by using a de-rotator attached to the eyepiece focuser, but this requires an additional motor and adds additional complexity and expense to the instrumentation. Argyle (p. 286) and Napier-Munn (p. 22) both point out that the rate of field rotation observed in altaz mounted telescopes is greatest at the zenith and zero when a star crosses the prime vertical, that is, when the star is due east or due west. As a result, initial double star measurements were conducted in an easterly direction and between altitudes of about It will be shown in this study that if simple adjustments are made to the reticle eyepiece of an alt-az telescope during double star data collecting, excellent results can be achieved in separation and position angle measurements that closely agree with data obtained with traditional equatorial telescopes. Equipment Used The telescope used in this research was an Obsession f/ inch Newtonian telescope with a Dobsonian (or alt-az) mount. It was equipped with a ServoCAT tracking and GOTO system made by StellarCAT. This system is controlled with a Wildcat Argo Navis computer. The Meade 12.5 mm astrometric eyepiece was used for all double star measurements. A RadioShack LCD Stopwatch with 0.01 second resolution was used to calibrate the linear scale of the Meade eyepiece. The observation sessions were held in San Luis Obispo, CA and Atascadero, CA. San Luis Obispo is located at latitude N, altitude 360 feet, in an area where light pollution is extensive and an evening marine layer limits the time of effective seeing. Atascadero is located approximately 15 miles north of San Luis Obispo at N, altitude 1050 feet, in an area of limited light pollution and no marine layer. Calibration of the Meade Astrometric Eyepiece The linear scale of the reticle eyepiece must be calibrated to the telescope being used. To determine the number of arc seconds per division, Argyle (p. 152) recommends using a star of medium brightness (magnitude 5-6) with a declination of and allowing it to pass along the length of the linear scale. This is carefully timed to the nearest 0.01 seconds. To reduce random errors in the process, 8-10 different drift times were recorded and the average determined. The average drift time is used in the following equation: T avg cos( δ RS ) Z = D where Z is the scale constant in arc seconds per division, T avg is the average drift time of the reference star across the scale in seconds, is the sidereal motion in arc seconds per second of Earth s rotation, cos(δ RS ) is the cosine of the declination of the reference star, and D is 50, the number of divisions for the Meade eyepiece Both Alpha Cephei (Alderamin) and Gamma Cassiopeiae (Navi) were used as calibration stars, depending on the time of the year the observations were conducted. Typical examples of the calibrations are indicted in Table 1. The units for the scale constant are arc seconds per division (a.s./div). Procedure for Measuring Separation After determining the scale constant for the Meade astrometric eyepiece, the telescope was twostar aligned and the tracking motors engaged. The primary star was centered in the eyepiece and the

29 Page 61 Visual Double Star Measurements with an Alt-Azimuth Telescope Star Bess. Epoch Dec. ( ) # Obs. Av Drift Time(sec) Std. Dev. Mean Error Scale Constant (a.s/div) α Cephei B γ Cass B Table 1: Determination of the scale constant eyepiece rotated so that both stars were co-aligned on the linear scale. The number of divisions between the stars was noted and estimated to the nearest 0.1 division. The slow motion control on the ServoCAT was then used to move the double star along the scale to a new location and another reading recorded. This was done to reduce the random error in assigning the number of divisions. Usually, no fewer than 10 readings were recorded and the average number of divisions calculated. The separation in arc seconds was calculated by multiplying the scale constant, Z, by the average number of divisions between the double stars. Procedure for Measuring Position Angle Initial Attempts Initial position angle measurements mimicked procedures used with equatorial mounted telescopes. The slow motion controls were used to center the primary, or brightest, star of the double star on the center mark of the linear scale, i.e. on the 25th division. Due to the presence of backlash, this was tedious, frustrating, and not always successful. Then the eyepiece was rotated, ensuring the stars were aligned on the linear scale. This sometimes resulted in having to re-center the primary star. If successful alignment was achieved, the servo-motors were disengaged and the double star allowed to drift to the edge of the eyepiece. As the primary crossed the outer protractor scale, the position angle was noted and recorded. The eyepiece was rotated 180 to prevent random errors of alignment. Then the procedure of two-star alignment was repeated using the Argo Navis computer, the primary star centered in the eyepiece, the secondary star aligned on the linear scale, and the motors disengaged. This procedure was time consuming, especially the centering of the primary star. It was tempting to use an off-centered primary that was close enough, which would have resulted in an erroneous position angle. It was necessary to find another technique of accurately centering the primary star. Final Procedure Adopted Instead of doing repetitive two-star alignments with the Argo Navis computer after every position angle measurement, the tracking motors were disengaged after the separation measurements were conducted. This allowed manual movement of the telescope. The eyepiece was rotated until the double stars were aligned on the linear scale. Then the telescope was moved so that the primary star accurately drifted through the central division mark. In practice, the primary was situated about 5-8 division marks away from the central mark and allowed to drift. If the star drifted through the central mark, the drift sequence was allowed to continue until the primary star passed across the outer protractor scale, and the angle recorded. If it missed the central mark, the scope was moved and another pass was attempted. This was much more successful and efficient than the former method. Also, after the position angle was recorded, the telescope was moved immediately until the star was repositioned in the center of the field of view. The reticle eyepiece was rotated 180 after every other drift measurement to allow constant realignment of the double stars with linear scale. Of course 180 had to be subtracted from half of the measurements so correct position angles were evaluated. This eyepiece rotation cancelled random errors that could have occurred if the eyepiece had been left in a single orientation. The majority of the known and neglected double stars selected for this study had separations greater than 34 arc seconds. Only one double star, Eta Casseopeiae, with an observed separation of 12.8 arc seconds, was included, since this was one of the initial trials performed. It was determined that any separation spanning less than 3 divisions on the linear scale made it very difficult to align the stars for position angle drift. If double stars with separations less than about 30 arc-seconds were to be studied, a Barlow lens should be employed. Indeed, Napier-Munn (p.25) found the use of a Barlow problematical except with

30 Page 62 Visual Double Star Measurements with an Alt-Azimuth Telescope Separation(arc seconds) Position Angle(degrees) Double Star Bess. Epoch # Obs. SD/ME Obs. Sep. Lit. Sep. ΔSep. # Obs. SD/ME Obs. PA Lit. PA ΔPA Lit. Epoch Pi And B / / WDS2006 Eta Cas B / / WDS2005 Table 2: Separation and Position Angle for Pi Andromedae and Eta Cassiopeiae separations of 3 divisions or less on the reticle. All observations in this study used just the Meade astrometric eyepiece alone. Results and Analysis of Observations Known Double Stars Table 2. lists the results obtained for the two initial double stars studied. These observations were performed in San Luis Obispo, CA. Due to a lingering marine layer and light pollution in the city, only bright double stars were investigated. Pi Andromedae, m1:m2, 4.3:7.1, and Eta Cassiopeiae, m1:m2, 3.5:7.4, were appropriate initial studies, except for the fairly small separation for Eta Cassiopeia. The observed separation and position angle are listed with their corresponding standard deviations (SD) and mean errors (ME). The columns headed ΔSep and ΔPA indicates the differences between the observed and literature values for separation and position angle, respectively. The telescope was moved farther from the effects of coastal fog and light pollution of San Luis Obispo 15 miles north to higher elevation and drier, darker skies in Atascadero, CA at Hill House Observatory. Longer observation sessions with steadier skies were possible due to this move. Five additional known double stars were measured at this location. Table 3 lists the results of the separation and position angle (PA) measurements, along with the standard deviations (SD) and mean errors (ME) for the number of observations recorded. The values for separation and position angle obtained in the current study for Mu Herculis and STF 698AB closely compare to other recent observations. See Tables 4 and 5. Neglected Double Stars Five neglected double stars were measured at Hill House Observatory. Table 6 lists the results of the separation and position angle measurements, respectively, along with their statistical evaluations. Conclusions The purpose of this study was to attempt separation and position angle measurements of known and neglected double stars with an alt-az mounted telescope. Prior investigations strongly recommended equatorial mounted telescopes be used for such studies due to the field rotation observed in alt-az mounted telescopes. It was suggested that separation measurements could be easily and accurately performed using the ServoCAT/Argo Navis control system with an alt-az telescope. Initial position angle measurements were attempted by using the handpad controls on the Servo- CAT/Argo Navis system to center the primary star, but the jerky backlash that occurred made it difficult and frustrating to try to center the primary star on Separation(arc seconds) Position Angle(degrees) Double Star Identifer Bess. Epoch # Obs. SD/ME Obs. Sep. Lit. Sep. # Obs. SD/ME Obs. PA Lit. PA Lit. Epoch Tau Tau B / / WDS1999 Mu Her B / / WDS2000 Beta Cam B / / WDS2003 STF 698AB B / / WDS2004 FRK B / / WDS1998 Table 3: Separation and Position Angle for Five Known Double Stars

31 Page 63 Visual Double Star Measurements with an Alt-Azimuth Telescope Year Separation Position Angle Source Comellas Comellas Year Separation Position Angle Source Comellas Comellas Schnabel Rojo Frey Frey Table 4: Separation and Position Angle for Mu Herculis since 1973 the middle division of the linear scale of the reticle eyepiece. When the servo-motors were disengaged and the primary star manually moved into a position where the star could drift through the center division, accurate and precise position angles could be repeatedly recorded. To verify that alt-az mounted telescopes could be used to make accurate measurements on double stars, seven double stars with known fixed separations and position angles were observed and compared to literature values. The differences in separation and position angles (DSep and DPA, respectively) and the percent differences between the observed and literature values for five of the seven known double stars studied are given in Table 7. Negative values indicate the observed value was less than the literature value; positive values indicate a greater value than literature. The low values shown in Table 7 indicate that the observed values for separation and position angles are very close to the literature values demonstrating that alt-az mounted telescopes can be used for accurate and precise measurements of double stars. The larger values for difference and % difference for Beta Cam Table 5: Separation and position angle for STF 698AB since 1970 may be explained by sky conditions. The double star was observed in the evening at the low altitude of 16 and it was windy. Five neglected double stars were then observed. The differences and percent difference between observed and literature values for these double stars are given in Table 8. Negative values indicate the observed value was less than the literature value; positive values indicate a greater value than literature. Again, the low percent differences for most of the neglected double stars in Table 8 demonstrate the accuracy of the alt-az system. It should be noted that percent differences for BUP 91AC and STT 23AC separations are prominently larger than the other neglected double stars studied. The reason for this difference was pointed out by Dave Arnold (personal communication). Arnold stated that BUP 91AC and STT 23AC are both composed of multiple star systems. For STT 23 the A and B components are in common proper motion but the C component is a background star having no physical connection to A and B. So the difference in separation between A and C in the current study (50.1 ) to that observed in 1909 (56.97 ) is due to proper motion from component A, Separation(arc seconds) Position Angle(degrees) Double Star Identifer Bess. Epoch # Obs SD/ME Obs. Sep. Lit. Sep. # Obs. SD/ME Obs. PA Lit. PA Lit. Epoch BU 492AC B / / WDS2000 BUP 91AC B / / WDS1929 STF 10AC B / / WDS2000 STT 23AC B / / WDS1909 STF 70AC B / / WDS1985 Table 6: Separation and Position Angle Measurements for Five Neglected Double Stars

32 Page 64 Visual Double Star Measurements with an Alt-Azimuth Telescope Double Star D Sep (arc secs) Sep % Difference not by orbital motion. He also states that BUP 91AC form an optical double star, because the proper motion vectors of these stars diverge. The values of the A component are -208 mas/yr (milliarc seconds/ year) in right ascension and -275 mas/yr in declination. The values for the C component are +8 and -25 mas/yr, respectively. Again, this was due to the proper motion of component A compared to the background star, C. Standard deviation and mean error analysis for drift times across the linear scale, estimated divisions between the double stars, and drift positions measured on the protractor were calculated. These statistics, summarized in Table 9, were used in determining the scale constants, separations, and position angles (PAs), respectively. Except for an elevated standard deviation value for the position angle of the known stars, all other statistics have very low values, indicating a fairly precise series of observations. The larger standard deviations for the position angles of the known double stars are probably the results of the author s initial inexperience in making these measurements. The drift method used for position angle measurement took quite a bit of practice to position the telescope so the primary star drifted through the exact center of the eyepiece. Initial attempts were slightly off the mark. Also, as the primary star drifted across the field of view and crossed the outer protractor scale, a parallax was observed. Different values of the position angle were detected depending on how you looked through the eyepiece. It took several sessions before I knew D PA (degrees) PA % Difference Tau Tau Mu Her Beta Cam STF 698AB FRK Average Table 7: Differences and % Differences between Observed and Literature Values for Separation and Position Angles of Five Known Double Stars Double Star exactly where to position my eye to get precise results. New Directions with an Alt-Az Telescope At Hill House Observatory, the lower limit of visual perception was estimated to be magnitude 12. Such stars could only be seen using averted vision. This was most challenging when position angle measurements were attempted. The star would disappear behind the main line of the linear scale. To visualize the star, one had to look about 5-8 division marks above or below the linear scale and estimate the corresponding measurement. Two ways of solving this problem come to mind. First, although Hill House was excellent for double star observation for magnitude 10 and less, a darker site would improve the ability of seeing these very faint stars. There was still some light pollution from the city lights of Atascadero. Second, use of the Celestron Micro Guide eyepiece instead of the Meade astrometric eyepiece is suggested. The Celestron model has two parallel lines running the length of the linear scale instead of just the single line on the Meade model. Faint stars would be more visible between the two lines than behind or on a single line. The light generated by the illuminated reticle can also prevent the detection of faint stars. The eyepiece has an adjustable switch that can vary the amount of illumination desired. But it can only be dimmed to a certain level. This minimum intensity may still interfere with seeing faint stars. This problem can be solved by purposely using weak batteries or by placing a piece of aluminum foil between the battery and the D Sep (arc secs) Sep % Difference D PA (degrees) PA % Difference BU 492AC BUP 91AC STF 10AC STT 23AC STF 70AC Average Table 8: Differences and % Differences between Observed and Literature Values for Separation and Position Angles of Five Neglected Double Stars

33 Page 65 Visual Double Star Measurements with an Alt-Azimuth Telescope Double Star Type SD for all separations SD for all PAs ME for all separations ME for all PAs Known <0.20 <2.80 <0.07 <1.00 Neglected <0.25 <1.10 <0.08 <0.32 Table 9: Standard Deviation (SD) and Mean Error (ME) Trends for Separation and Position Angle Measurements Determined for Known and Neglected Double Stars. electrical contact on the battery case. Both methods will reduce the illumination of the reticle eyepiece. Double stars with separations greater than 30 were chosen for the current paper. It is difficult to get repeatedly accurate alignment of the double stars on the linear scale for position angle measurements of less than three divisions. To measure double stars with smaller separations than 30, a Barlow lens should be employed. A 2x or 5x Barlow will magnify the separation and make division estimates easier. However, if the seeing is marginal, as it often is in coastal regions, the Barlow will magnify the seeing problems as well. Such studies should be done at dark sky sites when the sky is very steady. Acknowledgements There are many people I want to thank for assistance in this study. Russ Genet, Professor of Astronomy at Cuesta Community College and Research Scholar in Residence at California Polytechnic State University, recently showed me that an 18 alt-az Newtonian telescope can be used in scientific research of double stars and is not just relegated to observation of deep sky objects at monthly club star parties. Whole new frontiers are now open to those with alt-az telescopes, thanks to his insight. A big thanks goes to Jim Carlisle and wife Pat for allowing me to set up my telescope in the much drier and darker site at Hill House Observatory and for help generating many star charts. I want to thank Tom Smith of Dark Ridge Observatory in New Mexico for sending me information on double stars and helping me decipher the double star catalogs. Finally, I really appreciate the help provided by Russ Genet, Jo Johnson, Vera Wallen, Tom Smith, Dave Arnold, R. Kent Clark, Bob Buchheim, and Jim Carlisle for reviewing this paper and for all their suggestions. A special thanks goes to Dave Arnold for his insight on the neglected stars BUP 91AC and STT 23AC. References Observing and Measuring Visual Double Stars, Robert Argyle, Springer, London Johnson, Jolyon M. and Genet, Russell M., Fall 2007,, 3, Napier-Munn, Tim, 2007, The Webb Society Double Star Section Circulars, 15, Tanguay, Ronald Charles, 1999, Sky and Telescope, February, Teague, Thomas, 2000, Sky and Telescope, July, Thomas G. Frey is Professor Emeritus of Chemistry at California Polytechnic State University in San Luis Obispo, CA. He has been an active member of the Central Coast Astronomical Society for over 25 years.

34 Page 66 Divinus Lux Observatory Bulletin: Report 13 Dave Arnold Program Manager for Double Star Research 2728 North Fox Fun Drive Flagstaff, AZ Abstract: This report contains theta/rho measurements from 99 different double star systems. The time period spans from to Measurements were obtained using a 20-cm Schmidt-Cassegrain telescope and an illuminated reticle micrometer. This report represents a portion of the work that is currently being conducted in double star astronomy at Divinus Lux Observatory in Flagstaff, Arizona. A number of months ago, I became involved in working with some of the data that is contained in the CD version of the Washington Double Star Catalog, which has a greatly expanded list of double stars that is not contained in the version. While in the process of doing this, I have noticed that the magnitude listings for the various double stars are more accurate than in the version. There are also far fewer discrepancies between the listings in the version and what is actually observed at the telescope. Because these updates have made the catalog easier to use, I would like to express my appreciation to all of those who have labored to enhance the accuracy of this data. An additional observation that could be made pertains to neglected doubles, which I have highlighted in a previous article. As was the case with the version, the version still contains a number of very neglected pairs that need measurements, but that exceed the capabilities of my instrumentation. One such example is HJ 764 ( ), which is listed with one measurement made in 1820! The components have a rho value of 21 and magnitudes of and The frustration is that while double stars like this are viewable in my telescope, the companion star is too faint for me to measure when using an illuminated reticle micrometer. The reason for mentioning this, again, is that researchers with larger telescopes would have the capability to provide such measurements. This could be of some importance since I have viewed a number of pairs, like HJ 764, that exceed the limits of my instrumentation and have had no published measurements for many decades. The fact that these types of double stars still appear in the version of the WDS catalog indicates that there is still a lot of valuable work to be done by those who are equipped to do it. It could be quite rewarding to be the first person to publish measurements of a neglected double star, like HJ 764, in almost 200 years! As has been done in previous articles, the selected double star systems, which appear in this report, have been taken from the version of the Washington Double Star Catalog, with published measurements that are no more recent than ten years ago. Several systems are included from the version of the WDS. catalog as well. There are also some noteworthy items that are discussed pertaining to the following table. As in previous reports, several double stars are identified as having undergone significant theta/rho shifts since the last published measurements were made. First of all, two double star systems have displayed increases in the rho values, since 1998,

35 Page 67 Divinus Lux Observatory Bulletin: Report #13 because of proper motions by both components. For HDS 478, this increase amounts to 5%, while in the case of ES 167, a 7% increase has been detected. Next, an increase in the theta value has been noted for BU 314 AB-C, amounting to about 2 degrees since Proper motions by the AB components are responsible for this. Another theta value shift, amounting to a decrease of around 2 degrees, has been measured for ARG 66. Proper motion by the companion star has caused this change to take place over the past decade. Proper motions by the reference point stars, for two selected double stars, have resulted in noteworthy rho value increases as well. For STF 436, a 2.6% increase in the rho value has occurred since 1998, while for HLD 84 AB, an 8.6% increase has been detected over the same time period. Another rho value increase, worthy of mention, pertains to ROE 28AB. For this double star, proper motions by both components have caused a 7.4% increase since Lastly, rho value increases for three additional double stars are significant enough to highlight. In the case of BAL 182, proper motion by the reference point star has caused a 2% increase to occur since For STF 1133, an 11% increase in the rho value has been measured. Proper motion by the reference point star is responsible for this shift over the past ten years. The final rho value increase of note, in this report, pertains to HJ 767 AB. For this pair, proper motion by the B component has caused a 3% increase to occur since NAME RA DEC MAGS PA SEP DATE N NOTES STF n 1 STF n 2 STF n 3 H 117AB n 4 STF n 5 STF n 6 STF n 7 STF n 8 STF n 8 STF n 10 HJ n 11 AG 70AB n 12 FRK n 13 KU n 14 HDS n 15 ES n 16 AG n 17 HLD 66AD n 18 SEI n 19 HJ n 20 STF n 21 Table continued on next page

36 Page 68 Divinus Lux Observatory Bulletin: Report #13 NAME RA DEC MAGS PA SEP DATE N NOTES ARG 100AB-C n 22 HJ 342AB n 23 GAL n 24 ES 2606AC n 25 ES 1522AC n 26 GAL n 27 BRT n 28 AG n 29 STF n 30 HJ 5461AB n 31 S n 32 STF 565AC n 33 STF n 34 HJ 346AB n 35 STF 588AC n 36 HJ n 37 BU 314AB-C n 38 STF n 39 HJ 3265AB * n 40 STT n 41 TOB 22AC n 42 STF 648AB n 43 STT n 44 BU 1006AC n 45 AG 92AB n 46 HJ 2253AC n 47 HJ 2260AB n 48 STF n 49 SEI n 50 WNC 2A-BC n 51 H n 52 GAL n 53 STF n 54 * Companion star is the brighter component. Table continued on next page

37 Page 69 Divinus Lux Observatory Bulletin: Report #13 NAME RA DEC MAGS PA SEP DATE N NOTES BUP 79AC n 55 BLL 15AD n 55 STF 716AB n 56 STT n 57 STF 711AB n 58 STF n 59 STF 738AB n 60 STF 738AD n 60 GUI 9AE n 60 SEI n 61 STF n 62 ARA n 63 STF 785AB n 64 STT 116AD n 64 STT n 65 STF 804AB n 66 GAL n 67 BUP n 68 J n 69 BRT n 70 STF 832AB n 71 H n 72 DUF n 73 STF n 74 HJ n 75 STF n 76 AG n 77 J 1949AB n 78 J 910AC n 79 STF n 80 WFC n 81 STF 928AB n 82 HDS n 83 Table continued on next page

38 Page 70 Divinus Lux Observatory Bulletin: Report #13 NAME RA DEC MAGS PA SEP DATE N NOTES HJ n 84 HLD 84AB n 85 AG n 86 STF1057AB-C n 87 ARG n 88 ROE 28AB n 89 STF1077AB * n 90 BAL n 91 STF n 92 ENG 32AC n 93 STF1118AC n 94 BU 200AC n 95 HO 245AC n 96 STF n 97 KU 95AB n 98 HJ 767AB n 99 * Companion star is the brighter component. Table Notes 1. In Eridanus. Common proper motion; p.a. decreasing. Spect. F5, F5. 2. In Eridanus. Relatively fixed. Common proper motion. Spect. F7V, F5V. 3. In Perseus. Position angle decreasing. Spect. A0, K. 4. In Aries. Common proper motion. Sep. dec.; p.a. inc. Spect. G5. 5. In Perseus. Relatively fixed. Common proper motion. Spect. B9V, B9. 6. In Aries. Relatively fixed. Common proper motion. Spect. G5, G5. 7. In Perseus. Relatively fixed. Spect. G8III, G8III. 8. In Taurus. Relatively fixed. Common proper motion. Spect. A2V, A0. 9. In Taurus. Common proper motion. Sep. & p.a. increasing. Spect. G8V, G5IV. 10. In Eridanus. Sep. & p.a. increasing. Spect. F5IV, K In Camelopardis. Common proper motion; sep. increasing. Spect. F8, F In Perseus. Common proper motion; p.a. increasing. Spect. A5, A In Perseus. Position angle increasing. Spect. G In Perseus. Position angle increasing. Spect. A2.

39 Page 71 Divinus Lux Observatory Bulletin: Report # In Eridanus. Sep. & p.a. increasing. Spect. F0, F In Perseus. Sep. increasing; p.a. decreasing. Spect. G In Taurus. Relatively fixed. Common proper motion. Spect. G In Eridanus. Separation slightly increasing. Spect. F In Perseus. Position angle decreasing. Spect. K In Eridanus. Separation slightly decreasing. Spect. F In Eridanus. Common proper motion; sep. & p.a. increasing. Spect. K5, K In Camelopardis. Slight increase in position angle. Spect. A4V. 23. In Eridanus. Sep. & p.a. decreasing. Spect. K3III. 24. In Eridanus. Position angle increasing. 25. In Perseus. Separation slightly increasing. Spect. B In Perseus. Separation slightly decreasing. Spect. K In Eridanus. Sep. decreasing; p.a. increasing. Spect. G In Eridanus. Separation and position angle slightly increasing. 29. In Perseus. Relatively fixed. Common proper motion. Spect. K In Taurus. Position angle slightly decreasing. Spect. B9IV, B9IV. 31. In Taurus. Position angle decreasing. Spect. B In Perseus. Sep. decreasing; p.a. increasing. Spect. F5, B In Perseus. Sep. & p.a. decreasing. Spect. K In Eridanus. Relatively fixed. Common proper motion. Spect. F In Taurus. Sep. & p.a. decreasing. Spect. A2V. 36. In Eridanus. Sep. increasing; p.a. decreasing. Spect. G In Eridanus. Relatively fixed. Common proper motion. 38. In Lepus. Sep. & p.a. increasing. Spect. F3V. 39. In Orion. Common proper motion; p.a. slightly increasing. Spect. F0, F In Auriga (NGC 1778). Position angle slightly decreasing. Spect. B8, B In Auriga. Relatively fixed. Common proper motion. Spect. F8V, G In Auriga. Relatively fixed. Common proper motion. Spect. A2, B In Auriga. Common proper motion; p.a. decreasing. Spect. G5, G In Orion. Sep. & p.a. increasing. Spect. K0, K In Orion. Relatively fixed. Common proper motion. Spect. F2V. 46. In Auriga. Separation increasing. Spect. G In Auriga. Relatively fixed. Spect. B In Orion. Common proper motion. Sep. & p.a. increasing. Spect. B, B. 49. In Auriga. Sep. & p.a. slightly decreasing. Spect. A2V. 50. In Auriga. Sep. & p.a. slightly decreasing. 51. In Orion. Sep. increasing; p.a. decreasing. Spect. F6V. 52. In Orion. Separation slightly decreasing. Spect. B5V, K0.

40 Page 72 Divinus Lux Observatory Bulletin: Report # In Orion. Separation slightly increasing. Spect. A0, A In Auriga. Position angle slightly increasing. Spect. F Phi or 24 Aurigae. AC= p.a. dec. AD = sep. inc. Spect. AD = K3III, B Tauri. Sep. dec; p.a. inc. Common proper motion. Spect. B9V, B9V. 57. In Auriga. Sep. & p.a. increasing. Spect. G9III, K In Auriga. Common proper motion. Sep. & p.a. decreasing. Spect. G1, K In Taurus. Relatively fixed. Common proper motion. Spect. B7III, B7III. 60. Lambda Orionis. AB = relfix; cpm. AD/AE = relfix. Spect. O8, B.5V, B9, B In M 36 in Auriga. Relatively fixed. Common proper motion. 62. In M 36 in Auriga. Relatively fixed. Common proper motion. Spect. B2, B. 63. In Auriga. Position angle increasing. Spect. G In Taurus. AB = sep. inc; p.a. dec. AD = relatively fixed. Spect. B In Taurus. Relatively fixed. Spect. K2, K In Orion. Relatively fixed. Spect. A In Lepus. Position angle increasing. Spect. A0, A Orionis. Separation slightly increasing. Spect. B9IV. 69. In Taurus. Separation slightly decreasing. 70. In Lepus. Position angle increasing. Spect. F6V. 71. In Lepus. Position angle slightly decreasing. Spect. F0V. 72. In Monoceros. Relatively fixed. Spect. B In Gemini. Separation slightly increasing. Spect. G0, G In Orion. Relatively fixed. Common proper motion. Spect. A0, A In Monoceros. Separation increasing. 76. In Auriga. Separation slightly decreasing. Spect. F In Auriga. Common proper motion; sep. slightly increasing. Spect. G5, G In Monoceros. Position angle slightly decreasing. Spect. B In Auriga. Sep. & p.a. increasing. Spect. G In Auriga. Common proper motion. Position angle increasing. 81. In Auriga. Relatively fixed. Common proper motion. 82. In Auriga. Relatively fixed. Common proper motion. Spect. F5, F In Monoceros. Sep. & p.a. increasing. Spect. F In Lynx. Position angle slightly increasing. Spect. K In Monoceros. Sep. increasing; p.a. decreasing. Spect. A In Auriga. Position angle increasing. 87. In Canis Major. Relatively fixed. Common proper motion. Spect. F5V. 88. In Monoceros. Position angle decreasing. Spect. G, G. 89. In Canis Major. Separation increasing. Spect. A2V. 90. In Monoceros. Relatively fixed. Spect. A3, A In Monoceros. Separation increasing.

41 Page 73 Divinus Lux Observatory Bulletin: Report # In Lynx. Sep. & p.a. slightly increasing. Spect. F Monocerotis. Position angle increasing. Spect. F6III. 94. In Lynx. Sep. decreasing; p.a. increasing. Spect. A Geminorum. Sep. decreasing; p.a. increasing. Spect. K0III. 96. In Monoceros. Separation slightly decreasing. Spect. A3III. 97. In Monoceros. Sep. increasing; p.a. decreasing. Spect. A5, A In Gemini. Sep. & p.a. increasing. Spect. G In Monoceros. Separation increasing. Spect. A0. Comment from Brian Mason The acknowledgement of the work improving the WDS between the and editions is gratefully accepted. It is the work of many hands. First and foremost are my two USNO colleagues, Bill Hartkopf and Gary Wycoff. Also work by other professionals and amateurs in locating and measuring neglected pairs has also markedly improved the database. In many cases pairs which are still neglected are going to be the ones which still have poor magnitude information, so cases like HJ 764, discussed here, are not uncommon. Table continued on next page

42 Page 74 Measurements of 61 Cygni (STF2758AB, WDS ) Wolfgang Vollmann Dammaeckergasse 28/D1/20, A-1210 Wien, Austria Abstract: I present results of measuring the proper motion of 61 Cygni using position measurements made over a period of 1 1/2 years. Between May 2006 and November 2007 I imaged the double star 61 Cygni (STF2758AB). I used my refractor with 130 mm diameter objective with a focal length of 1040 mm and a CCD camera, SBIG ST237A, with a pixel size of 7.4 micrometer giving a scale of 1.47 arc seconds per pixel on the sky. My main goal was to measure the proper motion of the stars and eventually to detect their parallax like Friedrich Wilhelm Bessel did in 1838 [1]. On 28 nights during the 18 months, I took at least 30 images every night. Best results came with short exposure times of 1 second and ½ second. The images were measured using Astrometrica software by Herbert Raab [2] using the UCAC2 reference star catalog. Depending on sky conditions between 20 and 40 reference stars down to 14 mag could be used by the software to determine right ascension and declination of 61 Cygni A and B referred to the UCAC2 reference frame. My goal to detect proper motion was easily achieved, see figure 1. I was even able to detect the parallactic movement of both stars, so my measurement precision was quite good, see Figure 2. Figure 1: proper motion of 61 Cygni A and B plotted. On the x-axis are the seconds of right ascension, on y-axis the seconds of declination. The slight waviness of the proper motion is due to parallax.

43 Page 75 Measurements of 61 Cygni (STF2758AB, WDS ) Figure2: Change of declination of 61 Cygni A after removing proper motion for this star. On the x-axis is plotted the time of observation in years, on the y-axis is plotted the observed arc seconds of declination. Proper motion correction was applied. The parallactic movement is clearly visible as a sinusoidal wave. Plotted is also the expected motion of the star due to a parallax of arc seconds which fits the observations quite well. Using the formulae (16.1) and (16.2) in [3] I also calculated the distance and position angle from the means of every measurement series on these nights. On several nights I made two or more independent series in hope of improving precision. I plotted the distance and the PA and found that the slow increase of distance and PA due to the orbital motion of the pair was visible very well in the plots. To check my results I compared them to the ephemeris calculated from the elements in [4] (PkO2006b), using Brian Workman s spreadsheet [5]. Distance is represented satisfactorily by this ephemeris, but my position angles are consistently 0.4 to 0.5 degrees larger than the ephemeris gives, see Figure 3. In a discussion on the yahoo group binary-starsuncensored [6], several astronomers provided help in explaining the difference in PA. Thanks to James Daley and Florent Losse for providing their measurements of the pair which agree very well with mine. So errors in the measurement or reduction process are improbable. Ross Shuart discussed the measures and compared them to the Hipparcos results and several available elements. He found that Hipparcos measures and my results agree more with the elements by Josties 1981 given in [7]. I have calculated an ephemeris from these elements and plotted it also in figure 3 and 4. My measures in 2006/2007 (see Table 1) seem to be better represented by them. Conclusion: the orbital motion of 61 Cygni was easily measurable using CCD images with a focal length of only one meter over a time span of 1 ½ years. A CCD image of 61 Cygnii is shown in Figure 5. The ephemeris given by the elements from PkO2006b represents the distance measures very well but should be improved as suggested by the measures of position angle. (Continued on page 77)

44 Page 76 Measurements of 61 Cygni (STF2758AB, WDS ) Figure3: Measurements of the position angle plotted over time. The black line is a linear fit to my observations. Red line is from the values given by the elements from PkO2006b. Yellow line is from the values given by the elements by Josties Figure 4: Measurements of separation angle plotted over time. The black line is a linear fit to my observations. Red line is the values given by the elements from PkO2006b. Yellow line is the values given by the elements by Josties 1981.

45 Page 77 Measurements of 61 Cygni (STF2758AB, WDS ) Year Separation (as) PA (degrees) Figure 5: CCD image of 61 Cygnii taken on July 20, North is up and the image size is approximately 16 x 12 arcminutes. (Continued from page 75) References [1] Bessel, Friedrich Wilhelm: Bestimmung der Entfernung des 61sten Sterns des Schwans. [2] Raab, Herbert: Astrometrica. [3] Argyle, Robert (ed): Observing and Measuring Visual Double Stars. Springer, [4] Hartkopf, William I. and Mason, Brian D.: Sixth Catalog of Orbits of Visual Binary Stars. [5] Workman, Brian: Binary Star Calculator. [6] group binary-stars-uncensored: [7] Worley, Charles: 4th Catalog of Orbits of Visual Binaries. Available from as catalogue V/39. Table 1: Measures of position angle and separation of STF2758AB:

46 Page 78 Observations of Selected Northern Neglected Double Stars Bob Koch Kochab Observatory Faribault, MN Abstract: Measurements of 21 neglected double stars from the United States Naval Observatory (USNO) Northern list. All observations and measurements were taken in the latter half of 2006 and early 2007 from my observatory located at North latitude & West longitude. Introduction The equipment I used for these observations was a 12 LX200 SCT f/10 telescope with a 12.5 mm Celestron MicroGuide eyepiece at 244x. The double stars chosen in this report were taken from the Washington Double Star (WDS) list of neglected double stars [1]. I chose doubles that were brighter than magnitude 12 and those doubles that had no observations for quite some time. Historical measurement data were provided by the UNSO [2]. Four separate measurements of position angle and separation were taken each night for each double star observed. All nights were then averaged out for the final measurement. Method As described in reference [3], a calibration was done on August 2, 2006 by timing the transit of Altair using my 12 LX200 SCT. Transparency and seeing were very good. Eleven measurements were taken and averaged between 1:00 AM and 2:00 AM on August 2, The declination of Altair is The average time of eleven transits was seconds. Using the formula s = t cos(δ)/d, a calibration constant of a.s. per division on the linear scale was obtained. Table 1 contains the calibration data. The new calibration was then tested on 5 known pairs whose separation and position angle have changed little in the last 100 years. [4] Table 2 contains a comparison of my measurements of the test pairs with the PA and separation from the WDS. After the calibration, I measured 21 neglected doubles. The measurements are given in Table 3. Acknowledgments I wish to thank Brian Mason and his team on providing timely historical data to me. References [1] Mason, Brian D. et al, US Naval Observatory. List of neglected double stars, Northern List. [2] Mason, Brian D. et al, US Naval Observatory. Observational List of historical observations, personal communication. [3] Bob Argyle, ed., Observing And Measuring Visual Double Stars, Springer, New York, 2004 [4] Ronald Charles Tanguay, The Double Star Observer s Handbook, The Double Star Observer, Table 1: Transit times in seconds. The average transit time is s, giving a calibration constant of as per division on the scale of the MicroGuide eyepeice.

47 Page 79 Observations of Selected Northern Neglected Double Stars Test Pair PA sep Measured PA Measured sep delta PA delta sep STF 39AB STF 37AB-CD STF 43Aa-B STF 307AB STF Table 2: Comparison of measurements of test double stars with PA and sep listed in WDS. WDS Name RA+Dec Mag PA (deg) SEP (as) Date N Notes STF 60 AB , STF 162 Aa-C , STF 296 AB , STF 307 AC , STF 484 AG , STF 484 AE , STF 484 AI , STF 484 EG , STF 484 EI , STF 516 AC , STH 5 AD , GUI 22 AB ,?? GUI 22 AD , STF 2692 AC ??,?? BU 697 AC , BU 697 AB , HJ 1741 AD , HJ 1741 AB , H 6 24 AB , H 6 24 AC , STT 511 AB , Table 3: Measurements of double stars. Notes: 1. No significant measurable change in PA or Sep 2. Only one other measurement taken in 1886 where the PA was measured at but no Sep was measured. My measures show a change in PA. I estimate the magnitude of the D star to be 10.

48 Page 80 Observations of Selected Northern Neglected Double Stars 3. A change in both PA & Sep has taken place since the initial measurements taken in My PA measure shows a 4 degree change. 41 historical measures show no PA change. The PA should be rechecked. 5. PA has changed 2.5 degrees, sep has not changed. 6. PA has changed by about 2 degrees, sep remains the same as the measurements taken in No measurement history available. 8. There have been 70 measurements taken and an orbit calculated. My measure seems to be off. 9. The PA has changed on this double by about 3.3 degrees. 10. The PA here has changed by 3 degrees. 11. The separation has changed by 3 since the last measurement in Because component C was so faint, it was tough getting a separation measure.

49 Page 81 Double Star Measurements Using a Webcam: Annual Report of 2007 Joerg S. Schlimmer Seeheim-Jugenheim, Hessen, Germany js@epsilon-lyrae.de Abstract: I report on the measurements of 58 double stars in 2007 using a standard webcam. The double star measurements reported here were made with an 8-inch Newtonian telescope. The primary focal length is only 800 mm. For observing double stars with separation more than 5 arc seconds, I enlarge the focal length up to 1500 mm by using a barlow system. For double stars between 1 and 5 arc second of separation, I enlarge the focal length up to about 3000 mm. To record the observations I use a standard webcam (Philips ToUcam pro 740 k). This webcam has a small CCD chip with square pixel of 5.6 x 5.6 micrometers. The resolution is 640 x 480 pixels. The reproduction scale of the optical system (focal length 1500 mm) is about 0.79 arc seconds / pixel or 0.34 arc seconds / pixel if a focal length of 3000 mm is used (Schlimmer 2007a). The faintest stellar magnitude which can be directly recorded is about For analyses of the webcam records I use the REDUC software package, written by Florent Losse. The version 3.74 or higher includes a separate module for loading AVI files and converts them into BMP files. This module is very helpful for webcam users like me, because I need no other software tool for analysis of webcam records. For double stars with components of equal brightness, the typical standard deviation is about 0.25 arc seconds by using the 0.79 arc seconds per pixel con- figuration. In cases of high contrast differences between the components like Vega (STFB 9AE) or Altair (STFB 10AC), the standard deviation is about 0.5 arc seconds. Anyway, reproduction tests show mostly better results. In some cases the signal to noise ratio is too low to analyze the frames. In those instances, the REDUC software can stack the frames. After stacking, the signal to noise ratio is much better with the result that the frame can be analyzed. The faintest magnitude of the stacked frame is 11.1 up to 11.5 magnitudes (e.g. STT 532). References Schlimmer 2007a, Double Star Measurements Using a Webcam, JDSO Vol. 3 No. 3 summer 2007 Schlimmer 2007b, Christian Mayer s Double Star Catalog of 1779, JDSO Vol. 3 No. 4 fall 2007 Table begins on next page.

50 Page 82 Double Star Measurements Using a Webcam: Annual Report of 2007 NAME RA+DEC MAGS PA SEP DATE N NOTES STFA notes 1 STF 205A-BC γ And STF 464AB Per STF 464AC Per STF 464AD Per STF 464AE Per SHJ 70AB Gemini STF1110AB Castor STF1196AB ζ Cnc STF1196AC STF1196AD S φ1 Cnc STF φ2 Cnc STF ι Boo STFB 6AB Regulus STF1424AB Algieba STF1424AC STF1424AD STF1424CD STF ξ UMa STF notes 2 STF Com SHJ 162Aa-B SHJ η Boo STF1864AB π Boo STF1888AB ξ Boo STF Boo H 3 7AC β Sco H 5 6Aa-C ν Sco STF2098AB Her STF2098AC STF2098AD SHJ 243AB Oph H Oph STF2272AB Oph H 5 39AB Vega STFB 9AE Vega Table continued on next page.

51 Page 83 Double Star Measurements Using a Webcam: Annual Report of 2007 NAME RA+DEC MAGS PA SEP DATE N NOTES H 5 36AC δ Sct STF2382AB STF2383Cc-D notes 3 STF notes 4 STF2474Aa-B notes 5 STFA α Vul BUP γ Aql STF2585AB-C ζ Sge STFB 10AB Altair STFB 10AC Altair STT 532AB β Aql STT 532AC STFA 50Aa-C /31 Cyg STF2703AB notes 6 STF2703AC STF2703BC STF2704AB-D β Del STF γ Del STF2758AB Cyg STF STF ζ Aqu STF notes 7 N = number of analyzed frames Notes : 1. STFA 1 = Mayer 1, introduced in Christian Mayer s Double Star catalog of 1779 (Schlimmer 2007b) 2. STF1633 = Mayer 32, introduced in Christian Mayer s Double Star catalog of 1779 (Schlimmer 2007b) 3. calibration star for focal length of 3000 mm 4. 3 degree north east of g Lyr, near STF degree north east of g Lyr, near STF STF2703AB = Mayer 66, introduced in Christian Mayer s Double Star catalog of 1779 (Schlimmer 2007b) 7. STF3050 = Mayer 80, introduced in Christian Mayer s Double Star catalog of 1779 (Schlimmer 2007b)

52 Page Observations with a CCD Camera and Various Telescopes Morgan Spangle Larchmont, NY msfainc@optonline.net Abstract: I report on the measurements of 77 double stars in 2007 using four different telescopes 2007 was a year of experimentation, as I changed equipment and software routines. For the measures on the following pages, I used four different telescopes: a Celestron 14 SCT; a Questar 7 Classic OTA; a Takahashi Mewlon 250; and a Celestron C9.25 SCT. I used a SBIG ST2000XM monochrome CCD camera to capture images of the targets. My observing routine did not change this year. I set up in my driveway, using a Takahashi NJP Temma 2 goto mount for the telescope. I used Astroplanner software to plan my observing session. The observing plans use the catalogs of neglected pairs from the U.S. Naval Observatory s WDS project. I use Software Bisque s suite of astronomy software (TheSky 6 Pro, Orchestrate, CCDSoft, Tpoint) to find the target, and control the mount and the camera. I imaged each target several times, taking at least 6 images each time; sometimes, I would visit a target several times in one night, other times, I would image a target over several different sessions spread over 2 to 7 nights. The number of images taken depended on seeing conditions at the time, as well as the delta magnitude and separation of the target. On average, about 40 images were used for each measure in the list. Some sample images are shown after the table of measurements. This year, I used Florent Losse s excellent software, REDUC, to analyze the images. Reduc requires use of a calibration star; my practice is to take images of a calibration star near the meridian at the start, middle and end of an observing session, to average out the variations in a night s seeing conditions should be another year of change. I am planning on building a roll-off roof observatory at a dark sky site about 2 hours north of my home, which I will operate remotely over the internet. Hopefully, this will make my observing time even more productive! DATE WDS NAME RA DEC PA SEP N NOTES ES h 35m 30s '16" ES h 43m 02s '35" ES 9 02h 46m 21s '46" ES h 49m 24s '13" ES h 51m 07s '57" ES h 51m 33s '29" Table continued on next page

53 Page Observations with a CCD Camera and Various Telescopes DATE WDS NAME RA DEC PA SEP N NOTES ES h 28m 32s '27" LARGE CHANGE MLB 16 03h 45m 40s '27" FOX h 46m 45s '27" MLB h 46m 48s '46" HJ h 33m 14s '32" ES h 00m 42s '53" HJ h 03m 18s '21" J 92 11h 59m 03s '50" HJ h 02m 56s '21" LDS h 12m 02s '09" STF h 16m 08s '37" ES h 16m 11s '55" HJ h 16m 32s '22" HO 52 12h 20m 43s '34" STT h 22m 17s '52" A 79 12h 27m 01s '04" BAL h 57m 31s '28" BU h 10m 47s '24" A 2585AC 13h 18m 54s '20" HJ h 32m 52s '47" HJ h 39m 21s '35" ES h 42m 28s '09" BU h 42m 54s '07" SKI 15 13h 52m 37s '13" RST3854AB 13h 55m 32s '23" HJ h 57m 11s '47" HO h 22m 38s '13" Table continued on next page

54 Page Observations with a CCD Camera and Various Telescopes DATE WDS NAME RA DEC PA SEP N NOTES ES h 39m 41s '50" ES h 43m 51s '03" HJ h 49m 30s '15" HJ h 10m 08s '27" ES 74 15h 17m 04s '08" LDS h 18m 59s '30" NDC11477 KZA 94 15h 31m 06s '00" KZA h 33m 58s '40" KZA h 34m 10s '51" KZA h 35m 36s '43" NDC11590 HJ 574AB 15h 50m 18s '00" NDC11610 HJ h 53m 00s '00" NDC11631 HJ h 57m 18s '00" HJ h 02m 51s '27" STF h 08m 55s '11" HO h 12m 25s '53" STF h 14m 41s '31" STF h 22m 17s '32" POU h 26m 19s '54" HO h 30m 54s '52" KZA h 44m 03s '36" KZA h 44m 19s '04" ES h 46m 34s '42" HJ h 04m 33s '27" WAL 76 17h 04m 44s '13" ES h 38m 54s '27" DRD 1 17h 41m 50s '54" Table continued on next page

55 Page Observations with a CCD Camera and Various Telescopes DATE WDS NAME RA DEC PA SEP N NOTES ES h 44m 22s '51" BU h 47m 52s '40" ES h 06m 55s '03" ES h 15m 52s '59" ES h 24m 48s '11" HU h 28m 38s '18" HJ h 28m 42s '44" HJ h 28m 47s '40" ES h 36m 20s '38" MLB h 41m 17s '19" SMA 97 19h 48m 38s '15" ES h 49m 00s '24" ES 23 19h 49m 59s '05" ES h 18m 26s '43" LEO 53 22h 29m 53s '00" STI h 30m 55s '12" HJ h 34m 12s '30" ES 74 DRD 1 ES 471 North is up, East to left in all images

56 Page Observations with a CCD Camera and Various Telescopes ES 962 ES 1089 ES 1250 HJ 2800 HO 406 KZA 94 KZA 101 MLB 526 STT 247 North is up, East to left in all images