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Filters
CGS4 Filters
The following two tables list the filters in use with CGS4, their
central wavelengths and cut-on and off wavelengths (half power). For the low resolution gratings, these filters are selected
automatically by the OT software. The CVF is used for order blocking with the echelle.
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 Throughput1 (%) |
| 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 |
| N52 |
1.293 |
1.283 |
1.305 |
66 |
2 The N2 and N5 filters are not currently installed in CGS4's filter
wheels.
These narrow band filters are no longer used in echelle mode as the CVF covers all available wavelengths. Unless otherwise indicated
however, they are still mounted in the CGS4 filter wheels.
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