2011-01-23

1

Auto-guiding System for CQUEAN

( CQUEAN 을 위한 2.1m Otto Struve 망원경의 자동 추적 장치 개발)

2010-10-08

Eunbin Kim

한국천문학회가을학술대회

1. About CQUEAN2. Otto Struve Telescope dynamics3. Expected number of stars

- expected magnitude - moving mechanism

4. Guiding Camera5. Agdr6. Point Source Test7. Perfomance Result

Contents

2011-01-23

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

– 1st step toward larger instrument projects

QSOs at z>7Brown dwarfs

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

2011-01-23

3

Summary of CQUEAN

• CCD Cameras– ANDOR iKon-M 934 BR-DD, 1024×1024 13μm pixels

(Science CCD camera)– FLI camera PL1001E (Guiding CCD camera)

• Filter system– 5 broadband filters, 1 intermediate-band, and1 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?

2011-01-23

4

2.1 m Otto Struve Telescope

2.1 m Otto Struve Telescope

2011-01-23

5

2.1 m Otto Struve Telescope

2.1 m Otto Struve Telescope

2011-01-23

6

2.1 m Otto Struve Telescope

2.1 m Otto Struve Telescope

2011-01-23

7

2.1 m Otto Struve Telescope

• 2 minute error

① 1.07 arcsec / 22.03 sec-> 0.05 arcsec / sec ( Red Line)

② 1.08 arcsec / 18.50 sec-> 0.06 arcsec / sec ( Red Line)

2.1 m Otto Struve Telescope

120s

2011-01-23

8

2.1 m Otto Struve Telescope

1.18 arcsec /2.41 sec(0.49 arcsec / sec)

1.50 arcsec / 8.52 sec (0.18 arcsec / sec)

1.40 arcsec / 4.43 sec(0.32 arcsec / sec)

2.1 m Otto Struve Telescope2.1 m Otto Struve Telescope

Can we have guiding

stars in the field ?

2011-01-23

9

CQUEAN System – Limiting Magnitude Calculation

• Equation of Limiting Magnitude

1.Sky Limited Case

2.Detector Noise Limited Case

mzp : zeropointg: gain [electron/ADU] S: SignalNpix : 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 18.17 limiting magnitude with using these equations.

t

BN

N

S

gm

g

electronSmm pixzpzp

1log5.2

][log5.2

0

1log5.2

][log5.2

n

N

t

R

N

S

gm

g

electronSmm pix

zpzp

CQUEAN System - Number of Guiding Stars

Limiting Magnitude (V) 18.17FOV 2.97´×2.97´

Ref. Allen, Astrophysical Quantities

0.0

0.1

1.0

10.0

10.0 11.0 12.0 13.0 14.0 15.0 16.0 17.0 18.0 19.0 20.0 21.0 22.0

Num

ber

of

Star

s

V mag

North Galactic Pole

South Galactic Pole

1.2

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.

2011-01-23

10

90 degree rotation part with robotic arm

Science camera

Guiding camera

Telescope

CQUEAN

CQUEAN System – Moving Mechanism

East :70 degree , West :20 degree

E

N

2011-01-23

11

CQUEAN System – Moving Mechanism

Motor: IMS, MDRIVE 34

Differential Decelerator:APEX, AD140-050Reduction gear ratio: 50

Guiding Camera

2011-01-23

12

Guiding System - Camera

FLI PL1001E 1024×1024

Pixel Size 24μm

Field of view 2.97´×2.97´

Pixel Scale 0.174 arcsec/pixel

Limiting Magnitude (V)

18.17

CCD type Front Illuminated

Readout noise 8e- RMS @ 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

2011-01-23

13

Agdr – control program

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.

Agdr

2011-01-23

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.

2011-01-23

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.

2011-01-23

16

Optical fiber - Input

Lab Test

Optical fiber - Output

FLI Image of artificial stars

Lab Test

2011-01-23

17

• 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

Test Process

Guiding performance Result

2011-01-23

18

CQUEAN on the telescope

First Light : Aug 10 , 2010 ~ Aug 17 , 2010

Result Image

GRB 100814 A - 1200s exp time

2011-01-23

19

NGC6633

W20E00E20

E40

E60

Image RA Dec

NGC6633 276.86591 6.7202513

W20 276.92280 6.7324411

E00 276.97931 6.7219161

E20 277.03117 6.6981125

E40 277.06969 6.6563109

E60 276.86591 6.7202513

Position Angle

W20-E00 19.7673172

E00-E20 20.0198557

E20-E40 19.7151083

E40-E60 19.4478627

2011-01-23

20

성능 분석• Aug .13 ~17. 2010• 5, 10, 60, 120,180, 300,1200 sec exposure images• FWHM changed in the error range

0

1

2

3

4

5

6

7

8

0 200 400 600 800 1000 1200 1400

Day13

Day14

Day16

Day17

Mea(16)

Exposure time (sec)

성능 분석

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0.5

0 500 1000 1500

Day16

Day17

Day14

Day13

Exposure time

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

0 500 1000 1500

Mean FWHM

Mean FWHM

Exposure time (sec)

2011-01-23

21

• 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 !

Result