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CGS4 Filters
JACH |JCMT |Computer Services |CGS4 
Up: CGS4Handbook 
 
 

CGS4 Filters

 
 
The following two tables list the filters in use with CGS4, their  central wavelengths and cut-on and off wavelengths (half power).
 

Broad Band Filters (for low and medium resolution gratings):

 
 
Filter Name Central Wavelength (µm) Cut-on Wavelength (µm) Cut-off Wavelength (µm) Throughput at Central Wavelength (%) Estimated Average Throughput (%)
IJ 0.94 0.84 1.04 55 48
B1 1.29 0.99 1.59 83 84
B2 2.02 1.43 2.60 92 89
B3 3.15 2.14 4.16 90 93
B4 3.50 2.75 4.24 90 88
B5 4.92 4.35 > 5.5 93 92
B6 2.21 2.00 2.41 78 74
 
1  Estimated in the central 75% of the bandpass.
 

 

Narrow Band Filters (echelle mode):

 
 
Filter Name Central Wavelength (µm) Cut-on Wavelength (µm) Cut-off Wavelength (µm) Throughput at Central Wavelength (%)
N1 1.089 1.078 1.099 57
N22 1.229 1.218 1.240 62
N3 1.259 1.247 1.272 62
N4 1.275 1.264 1.286 59
N5 1.293 1.283 1.305 66
 
 

2 The N2 filter is not currently installed in CGS4's filter wheels.
 

For wavelengths beyond  1.3-µm, the CVFs are used as order-blockers when using the echelle. When the new wedged CVFs are installed, the narrow band filters will no longer be necessary, as one of the CVF segments will extend down to 0.93 um.
 



Last Modification Date: 1998/08/04 - Last Modification Author: Tom Kerr
Tom Kerr (tkerr)
 
Contact: Tom Kerr. Updated: Wed Oct 6 11:58:03 HST 2004

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