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The Grism Wheel

There are two available grisms in the reimaged/spectrograph mode: 300 l/mm and 600 l/mm. There is no available tilt for the grisms, so the wavelength coverage for the standard longslits is fixed. See Table 6 for a description of the grisms.

It is possible to obtain a different center wavelength by constructing a longslit (or multislit) mask that is offset in the focal plane along the dispersion direction. See the section on making multislit masks for a description of how to do this.

Interference filters are best placed in a parallel beam, so that their appropriate place in this instrument is in the grism wheel. Judy Cohen has a filter holder for the grism wheel; see her to use it. The clearance at the top of the filter holder is small, so it requires shaving off the top of the screws.


Table 6
Grism Wheel
Position Grism

(l/mm)
Blaze

(Å)
Center
Wavelength
(Å)
Mean
Dispersion
(Å pixel-1)
1 300 5500 6500 ~3.1
2 clear, available      
3 600 4800 5000 ~1.46
4 clear, available      



next up previous
Next: Flat-field and Arc Lamps Up: User Manual for COSMIC Previous: Installation
Roy Gal
4/25/1998