Grism Selection Guide

Update: Feb 19, 2010

Resolution vs. Wavelength

Efficiency vs. Wavelength
VPH grisms other grisms (incomplete)

General Notes:

  1. The grisms shown in the blue panels below are ready for open-use. Others are being tested or under fabrication.
  2. Spectral resolution (R = l /dl ) is almost proportional to the slit width, w, if w is greater than 0.2". In the following table, w = 0.4" is adopted. Generally, wider slit degrades the spectral resolution, but raises the sensitivity when CCD binning is properly done along the wavelength direction.
Grism name Links to figures of efficiency, etc. Lines or Grooves (mm-1) Order Dispersion
(A/pix)
Center
WL
(A)
Spectral Resolution with 0.4" slit Order Cut
Filter
Wavelength
Coverage
(A)
0th order? 2nd order? Targets/Comments
Very low Efficiency
Design
Drawing
Holder
75 1 5.46 6500 250 SO58 5800-10000 YES NO Red MOS survey even @ >9400A
SY47 4700-9000 YES Overlap at >9000 Red MOS survey @ 4700-9400
L600 3650-6000 YES YES Blue MOS survey
L550 3400-5500 YES YES Blue MOS survey even @<3500A
Low Efficiency
Design
Drawing
[a] [b]
[1] [2] [3] [4]
150 1 2.72 6500 500 SY47 4700-9000 NO Overlap at >9000 Red Low disp.
SO58 5800-10000 NO NO No 2nd order contami. even @ >9500A
L600 3650-6000 NO YES Blue Low disp.
2 1.4   700 L550 3400-5500 NO YES Highest sensitivity for <3800A
Middle Blue Efficiency
Throughput1
Throughput2
Design
Drawing
Holder
300 1 1.34 5500 1000 SY47 4700-8300 NO YES - Red Mid disp
- Higher sens. than 300R @ <7800A
- >8400A out of CCD
SY47
offset slit
4700-9000 NO Overlap at >9000 Larger spectral coverage
L600 3650-6000 NO YES Blue Mid disp
LC50 3300-6000 NO YES(weak) Sensitive even @ <3500A
none 3650-8300 NO Overlap at >7000 - Blue Mid disp
- Higher efficiency
- contamination by scattered light at <3800A
Middle Red Efficiency
Throughput1
Throughput2
Throughput3
Design
Drawing
300 1 1.34 7500 1000 SY47 4900-9000 NO YES - Red Mid disp
- Higher sens. than 300B @ >7800A
- 4700-4900A out of CCD
O58 5800-10000 NO NO No 2nd order contami. even @ >9500A
2 0.67 3900 2000 L600 3650-5250 NO --- Higher sens. than 300B 2nd
L600
offset slit
3650-5950 NO ---
L550 3400-5250 NO --- - Sensitive even @ <3500A
- better blocking for 1st order contami.
Grism name Links to figures of efficiency, etc. Lines or Grooves (mm-1) Order Dispersion
(A/pix)
Center
WL
(A)
Spectral Resolution with 0.4" slit Order Cut
Filter
Wavelength
Coverage
(A)
0th order? 2nd order? Targets/Comments
High Echelle Efficiency
Throughput
Design
Drawing
Holder [1] [2]
175
(Echelle)
2 -0.98
@9300A
9720 2500 Cross Disp. 7900-10000 NO --- opposite dispersion direction (Note 2)
SDSS-z' 8300-10000 NO ---
I
offset slit
7300-8700 NO ---
3 -0.63
@6600A
6550 2500 Cross Disp. 5400-7900 NO YES
I 7300-7900 NO YES
R 5900-7100 NO YES
4   4980   Cross Disp. 4200-5900 NO YES
5   4040   Cross Disp. 3600-4600 NO YES
High 450 Throughput
Prism Drawing
Holder [1] [2] [3] [4] [5] [6]
1000
(VPH)
1 0.376 4500 4000 No filter 3800-5250 NO NO peak efficiency @ 4000A
x shift = +16 pixel (Note 1)
No filter
offset slit
4200-5650 NO NO
High 520 Throughput
Prism Drawing
Holder [1] [2] [3] [4] [5] [6]
1000
(VPH)
1 0.394 5250 4000 No filter 4450-6050 NO NO x shift = -47 pixel (Note 1)
No filter
offset slit
4900-6500 NO NO
High 650 Throughput
Prism Drawing
Holder [1] [2] [3] [4] [5] [6]
665
(VPH)
1 0.61 (average) 6500 2500 SY47 5300-7700 NO NO x shift = +222 pixel (Note 1)
SY47
offset slit
5950-8350 NO NO
2 0.28
@4000A
  3500 L600
offset slit
3650-4350 NO ---
LC50 3300-4350 NO ---
High 850   360
(VPH)
1 1.18 8000 1700 SO58 5800-10350 NO NO x shift = -6 pixel (Note 1)
SO58
offset slit
6850-11650 NO NO
High 900   555
(VPH)
1 0.74 9000 3000 SO58 7500-10450 NO NO x shift = -120 pixel (Note 1)
SO58
offset slit
8300-11300 NO NO
Very High 680 Throughput
Prism Drawing
Holder [1] [2] [3] [4] [5] [6]
1600
(VPH)
1 0.223 6900 8000 SY47 6450-7350 NO NO x shift = +41 pixel (Note 1)
SY47
offset slit
6700-7600 NO NO
Very High 800 Throughput
Prism Drawing
Holder [1] [2] [3] [4] [5] [6]
1324
(VPH)
1 0.282 8000 7000 SY47 7500-8600 NO NO - not tested for polarimetry
- x shift = -27 pixel (Note 1)
SY47
offset slit
7800-8900 NO NO
Very High
950
Efficiency
Throughput
Drawing
Prism drawing
Holder [1] [2] [3] [4] [5] [6]
1095
(VPH)
1 0.352 9500 6000 O58 8860-10200 NO NO - Unavailable for polarimetry
- x shift = -190 pixel (Note 1)
Grism name Links to figures of efficiency, etc. Lines or Grooves (mm-1) Order Dispersion
(A/pix)
Center
WL
(A)
Spectral Resolution with 0.4" slit Order Cut
Filter
Wavelength
Coverage
(A)
0th order? 2nd order? Targets/Comments

Note

  1. The VPH grisms produce image shifts along the slit direction (= orthogonal to the dispersion direction).
    The values listed above are in pixels for 1x1 binning (~0".1/pixel) where positive values denote that the shift direction is from CCD chip1 to chip2.
    The sign of this direction is opposite to that of "Shift_Sec" parameter in the "SetupField" command in OPE file.

  2. The dispersion direction of the High Echelle grism is opposite to other grisms.
    Therefore, the value of the dispersion is negative.