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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 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
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.

Contact: Tom Kerr. Updated: Thu Feb 24 15:30:08 HST 2005

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