Early Sciences &
Test observations
with LAMOST
Yongheng Zhao
National Astronomical Observatories of China
Characteristics of LAMOST
•
•
•
•
•
•
Effective aperture
FOV
Number of fibers
Observing sky area
Spectral resolution
Survey capability
• Size of fiber
•
Site seeing: ~2 arcsec
3.6-4.9 meter
5（1.75m linear）
4000
-10    +90
R=1000/2000 (+5000/10000)
spectral resolution 1nm,
integration time 1.5 hours,
magnitude limit: 20.5m
3.30 arcsec（ 320 macro linear）
Oct 20, 2007
Structure of LAMOST
Fiber
Positioning
MA
mirror
Fibers
MB
mirror
Spectrographs
CCDs
Optical System
MB
( ~ 6.1m)
 Segmented Active
optics
for 37 sub-mirrors of MB
（July 13,2008)
24 sub-mirrors of MA （~ 4.9m）
 Segmented
and thin
mirror active optics for
24 sub-mirrors of MA
（Sept. 10, 2008)
Image quality of LAMOST
Statistics
Image Quality vs Iteration
30
25
25
EE80(arcsec)
20
20
15
Times 15
10
10
5
5
0
1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 55 58 61 64 67
Iterations
(每次迭代约2分钟)
<1”
Target: < 2”
0
0.1 0.3 0.5 0.7 0.9 1.1 1.3 1.5 1.7 1.9 2.1 2.3 2.5 2.7 2.9 3.1
EE80(arcsec)
（Nov. 21, 2008)
At 5.2 degrees FOV
Oct. 11, 2008
At 3.2 degree FOV

FWHM<10pixel,
~2 arcsec
Apr.25, 2009
Image quality: 0.3-0.4 arcsec
Seeing: 1.7-2 arcsec
Pointing
< 5”
Target: < 10”
Tracking
0.632“（80%）
0.52"（rms）
Target: < 1”
Instruments

4000 Fibers (130km)
 4000 Fiber positioning units
 16 Spectrographs


250 fibers per spectrograph
32 4k x 4k CCD Cameras

E2V CCD chips
Focal Plate for holding 4000 fibers
8.
75
8.
单元1
Ø4
75
1
2
单元2
3
4
26
Double arm scheme
Positioning unit with 2 step motors
4000 fiber positioning units
Repeat accuracy of 4000 units
<0.14”
target: <0.5”
16 spectrographs
250 fibers per spectrograph
RL = 1000/2000
RM= 5000/10000
Spectral range:
Low
blue: 370—590nm
red: 570—900nm
Medium blue: 510nm — 540nm
red: 830nm — 890nm
16 spectrographs
Relative efficiency of fiber to fiber
（No.6 spectrograph-blue）
Efficiency of spectrograph
370~900nm

43% (peak)

Target ：35%（peak）
Test Observations
 Sept.
2008 – June 2009

Test observations for check

Several dark nights in each month
Spectra of bright stars（28/9/2008）
Blue
Red
Apr.1, 2009
Galaxies
(g>19)
Apr.1, 2009
QSOs
(g>19)
Apr. 26, 2009
 Stars
 More
(V<19)
than 3600 spectra got in one test
observation (>90% of selected objects)
No.5: red
No.4: red
Early Sciences
Test observations for scientific WGs
 Observations: 97 exposures (each 1.5h)





Oct. 2009: 20 for stars
Nov. 2009: 20 for stars, 6 for galaxies
Dec. 2009: 18 for stars, 10 for galaxies
Jan. 2010: 18
Feb. 2010: 7
Oct. 26,
2009
M31 area
M31
17 new PNs
 19 confirmed
two exp. in Oct. & Dec.

Beyond M31:
14 new QSOs：z<2
8 New QSOs
1 exp. In Dec.
Candidates of metal-poor stars


19 with S/N>15
9 with [Fe/H]<-1
Candidates of metal-poor stars

 8 MP stars
 Pipeline
1: [Fe/H]~-2.7
Improvement
 Mar.-July

Positioning accuracy for 4000 fibers
 Jul.-Sep.


Fine adjusting of spectrographs & CCDs
2D pipeline
Positioning accuracy for 4000 fibers
2”  1”
M31 area
Sep.11,
2010
Plan
 Oct.-Dec.

Scientific test observations
 Jan.-June

Test for scientific surveys
Thank You！
Positioning errors
 “fiber
scan”
July 6
σx=1.7”, σy=2.3”
ΔY (“)

ΔX (“)
Positioning of 4000 fibers
 Transformation


of Coords.
4000 coordinates for 4000 fibers
Fiber coords.  Focal plane coords
• 4000（x0，y0，θ0）

FP coords.  CCD coords.（celetial）
• Shift, rotation, expanding
 Symmetric

errors
measurement  correction
Coord. of 4000 fibers

Coord. of 4 guiding CCDs
Celestial coords measured by 4 guiding CCDs
CCD coords
Fiber coords
July 6


σx=1.7”, σy=2.3” 
σx=1.1”，σy=1.2”
Dome Seeing




日期：20091122
天区：06faint
中央星：124.7456700 56.2547100 7.00 3.70 8.40
Seeing：11*0.24= 2.64角秒（CCD：4033）（时间：
04:30)
•日期：20091221
•天区：sky5f
•中央星：91.0300674 23.2636089
5.09
0.00
0.00
•Seeing：8*0.24= 1.92角秒（CCD：6033）（时间：1:12)
光纤偏离和视宁度对极限星等的
影响
光纤偏离
-----------视宁度
0”
1”
2”
3”
4”
5”
1”
0.0m
0.1m
2.0m
8.0m
2”
0.2m
0.4m
1.6m
3.7m
7.0m
3”
0.6m
0.8m
1.6m
2.7m
4.3m
6.7m
4”
1.0m
1.1m
1.8m
2.5m
3.5m
4.8m
5”
1.4m
1.5m
2.0m
2.4m
3.2m
4.1m
圆顶杂散光测量
3月9日
光谱
仪
10
3月10日
Isc
Isc+Is Isc/Is
k
k
147
911 19%
Isc
Isc+Is Isc/Is
k
k
113
887 14 %
11
168
809
26%
133
705
23 %
12
153
827
22%
121
720
20 %
13
156
798
24%
129
705
22 %
14
143
900
18%
114
784
17 %
15
94
570
19%
78
581
15 %
光纤对准测定
单高斯
拟合：
x0，y0
FWHM
F*, Fb
焦平面调整（3月）
 光轴+焦平面
 共面



S-H中心（焦点）
4000光纤端面
4导星CCD靶面