Auto-guiding System for CQUEAN

Transcription

1 Auto-guiding System for CQUEAN ( CQUEAN 을위한 2.1m Otto Struve 망원경의자동추적장치개발 ) Eunbin Kim 한국천문학회가을학술대회 Contents 1. About CQUEAN 2. Otto Struve Telescope dynamics 3. Expected number of stars - expected magnitude - moving mechanism 4. Guiding Camera 5. Agdr 6. Point Source Test 7. Perfomance Result 1

2 CQUEAN Camera for QUasars in EArly universe Optical CCD camera optimized for observation of QSOs of 5.5< z <7.5 Deep-depletion CCD which is more sensitive at 1μm than conventional CCD g, r, I, z, Y, is,iz 1 st step toward larger instrument projects Why do we need red-sensitive instruments? Observation of high z QSOs Requires the NIR-range sensitive instrument, due to their extreme redshifts Feasible even with medium size telescope QSOs at z>7 Brown dwarfs 2

3 Summary of CQUEAN CCD Cameras ANDOR ikon-m 934 BR-DD, μm pixels (Science CCD camera) FLI camera PL1001E (Guiding CCD camera) Filter system 5 broadband filters, 1 intermediate-band, and 1 narrow-band filter Telescope 2.1m Otto Struve 2.1m Telescope at McDonald Observatory, USA 2.1m Otto Struve Telescope The status of the Otto Struve Telescope How good is the telescope tracking? 3

4 2.1 m Otto Struve Telescope 2.1 m Otto Struve Telescope 4

5 2.1 m Otto Struve Telescope 2.1 m Otto Struve Telescope 5

6 2.1 m Otto Struve Telescope 2.1 m Otto Struve Telescope 6

7 2.1 m Otto Struve Telescope 2.1 m Otto Struve Telescope 2 minute error arcsec / sec -> 0.05 arcsec / sec ( Red Line) 120s arcsec / sec -> 0.06 arcsec / sec ( Red Line) 7

8 2.1 m Otto Struve Telescope 1.40 arcsec / 4.43 sec (0.32 arcsec / sec) 1.50 arcsec / 8.52 sec (0.18 arcsec / sec) 1.18 arcsec /2.41 sec (0.49 arcsec / sec) Can we have guiding stars in the field? 8

9 CQUEAN System Limiting Magnitude Calculation Equation of Limiting Magnitude 1.Sky Limited Case m m zp S[ electron] 2.5log m g zp 1 2.5log g S N N pix B t 2.Detector Noise Limited Case m m zp S[ electron] 2.5log m g zp 1 S R 2.5log g N t N n pix 0 m zp : zeropoint g: gain [electron/adu] S: Signal N pix : number of pixels that cover a stellar profile B : sky background per pixel [electron/sec] t : exposure time [sec] R : readout noise [electrons] We get limiting magnitude with using these equations. CQUEAN System - Number of Guiding Stars 1.2 Limiting Magnitude (V) FOV Number of Stars We get expecting guiding stars 1.2 in north galactic pole. Although this number can be a minimum we need to secure larger field of view. The solution is moving mechanism of guiding system. North Galactic Pole South Galactic Pole V mag Ref. Allen, Astrophysical Quantities 9

10 CQUEAN System Moving Mechanism East :70 degree, West :20 degree Telescope Guiding camera Science camera 90 degree rotation part with robotic arm CQUEAN N E 10

11 CQUEAN System Moving Mechanism Motor: IMS, MDRIVE 34 Differential Decelerator: APEX, AD Reduction gear ratio: 50 Guiding Camera 11

12 Guiding System - Camera FLI PL1001E Pixel Size 24μm Field of view Pixel Scale Limiting Magnitude (V) CCD type Readout noise arcsec/pixel Front Illuminated 8e- 1Mhz For point source with 10σ level after 1hr integration with assumption of : Gain = 10e/ADU, Seeing=1.2, Optical transmissivity =80% Quantum efficiency of FLI PL1001E 12

13 Agdr control program Agdr Agdr is a software developed by Sam Odams for guiding system. It supports 2.7m telescope in McDonald Observatory. Modification of the program for 2.1m telescope is on progress. We will make artifitial stars as point sources and test the guiding system. Figure is the Guider History. 13

14 Agdr program Screen and Functions Chart EE50, Flux, FWHM, Magnitude, Scatter, Focus Comments Expose exposure, binning, auto save, overwrite Focus / Tip tilt Guider Guider History Instrument Setup position angle offset, ATOG position angle, flip axis in RA and Dec Scale min and max of the chart, CCD and sky Specify Fiducial location and nonsidereal offset TCS History TCS Offset View Contours View Parameters View Setup Etc. 14

15 Point Source Test Test Step 1. Make artificial stars. Ne-He laser is a light source and the light from the end of optical fibers will be 3~5 artificial stars. 2. Make a rectangle with a cursor and then it recognize the star and get information such as location, peak, flux, and magnitude.etc. 3. Start auto-guiding program. 4. Check the proceeding and modify the program. 15

16 Lab Test Optical fiber - Input Optical fiber - Output Lab Test FLI Image of artificial stars 16

17 Test Process Complete making 3~4 artificial stars. The program recognize the displacement of a star. But the auto guiding system doesn t work. Make TCS program and then it can communicate with the guiding program. We will confirm the auto guiding system works properly. -> plan changed not to use Agdr and make own program. -> plan changed again : Use Agdr Guiding performance Result 17

18 CQUEAN on the telescope First Light : Aug 10, 2010 ~ Aug 17, 2010 Result Image GRB A s exp time 18

19 E20 E00 W20 E40 E60 NGC6633 Image RA Dec NGC6633 W20 E00 E20 E40 E Position Angle W20-E00 E00-E20 E20-E40 E40-E

20 성능분석 Aug.13 ~ , 10, 60, 120,180, 300,1200 sec exposure images FWHM changed in the error range Day13 Day14 Day16 Day17 Mea(16) Exposure time (sec) 성능분석 Day Day Day Day Exposure time Mean FWHM Mean FWHM Exposure time (sec) 20

21 Result Exposure time of guiding camera: 1 sec, 2 sec, 5 sec Exposure time of science camera: 0.1 ~1200 sec Rotation from East 20 degree to West 70 degree Can t see Periodic error by 2 min worm gear Stable imaging! Stable guiding! 21