2011-01-23
Auto-guiding System for CQUEAN
( CQUEAN 을 위한 2.1m Otto Struve 망원경의 자동 추적 장치 개발)
2010-10-08
Eunbin Kim
한국천문학회
가을학술대회
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
2011-01-23
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
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
2011-01-23
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, 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
2011-01-23
2.1 m Otto Struve Telescope
2.1 m Otto Struve Telescope
4
2011-01-23
2.1 m Otto Struve Telescope
2.1 m Otto Struve Telescope
5
2011-01-23
2.1 m Otto Struve Telescope
2.1 m Otto Struve Telescope
6
2011-01-23
2.1 m Otto Struve Telescope
2.1 m Otto Struve Telescope
•
2 minute error
① 1.07 arcsec / 22.03 sec
-> 0.05 arcsec / sec ( Red Line)
120s
② 1.08 arcsec / 18.50 sec
-> 0.06 arcsec / sec ( Red Line)
7
2011-01-23
2.1
m
Otto
Struve
Telescope
2.1
2.1m
mOtto
OttoStruve
StruveTelescope
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
2011-01-23
CQUEAN System – Limiting Magnitude Calculation
• Equation of Limiting Magnitude
1.Sky Limited Case
1 S
 S [electron] 
  mzp  2.5 log
m  mzp  2.5 log
g


g N
N pix
B

t 
2.Detector Noise Limited Case
1 S R
 S[electron] 

m  mzp  2.5 log
  mzp  2.5 log g N t
g



N pix 

n0 
mzp : zeropoint
g: gain [electron/ADU]
S: Signal
Npix : 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.
CQUEAN System - Number of Guiding Stars
Limiting Magnitude (V)
FOV
18.17
2.97´×2.97´
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.
10.0
Number of Stars
1.2
1.0
0.1
North Galactic Pole
South Galactic Pole
0.0
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
V mag
Ref. Allen, Astrophysical Quantities
9
2011-01-23
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
2011-01-23
CQUEAN System – Moving Mechanism
Motor: IMS, MDRIVE 34
Differential Decelerator:
APEX, AD140-050
Reduction gear ratio: 50
Guiding Camera
11
2011-01-23
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
12
2011-01-23
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
2011-01-23
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
2011-01-23
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
2011-01-23
Lab Test
Optical fiber - Input
Optical fiber - Output
Lab Test
FLI Image of artificial stars
16
2011-01-23
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
2011-01-23
CQUEAN on the telescope
First Light : Aug 10 , 2010 ~ Aug 17 , 2010
Result Image
GRB 100814 A - 1200s exp time
18
2011-01-23
E00
E20
W20
E40
E60
NGC6633
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
19
2011-01-23
성능 분석
• Aug .13 ~17. 2010
• 5, 10, 60, 120,180, 300,1200 sec exposure images
• FWHM changed in the error range
8
7
6
5
Day13
Day14
4
Day16
3
Day17
Mea(16)
2
1
0
0
200
400
600
800
1000
1200
1400
Exposure time (sec)
성능 분석
0.5
Mean FWHM
5
0.45
4.5
0.4
4
0.35
3.5
0.3
Day16
0.25
Day17
0.2
0.15
0.1
3
2.5
2
Day14
1.5
Day13
1
Mean FWHM
0.5
0.05
0
0
0
500
1000
Exposure time
1500
0
500
1000
1500
Exposure time (sec)
20
2011-01-23
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