Echelle Spectrograph Filters Pre-slit and Post-slit

Pre-slit Filter Wheel

The pre-slit filter wheel (figure 1 ) contains six 2" x 2" (50.8 x 50.8mm) filters, used mainly for cross disperser order separation. Their use may be preferred to the post-slit filters as a collimator focus change may be required for the latter. Table 1 contains a list of these filters and figure 2 illustrates their transmission curves. A spare filter wheel is available for special filters or filters supplied by the observer.

 

Pre-Slit and Post Slit Filters
Position Filter thickness(mm)
pre-slit (2'' x 2'')
1 N.D - 2.5 mag 2
2 N.D - 5.0 mag 2
3 GG-385 2
4 GG-495 2
5 RG-610 2
6 CuSO4 6
7 open -
pre-slit (1'' x 1'')
1 N.D - 2.5 mag 2
2 N.D - 5.0 mag 2
3 GG-385 2
4 GG-495 2
5 RG-610 2
6 RG-695 2
7 optional* -
8 open -
* special 222 x 222 holder

Table 1: Pre-slit and post-slit filters