1.5mRC Filters

There are two filter wheels each with a clear position and space for four 38.1mm (1.5 inch) diameter filters. The pre-slit filter wheel contains neutral density filters with nominal attenuations of 1.5, 5.0 and 7.5 magnitudes. Note that the light from the comparison lamps does not pass through these filters. Standard order-sorting filters are normally available in the post-slit wheel. These filters can be changed with some difficulty while the spectrograph is on the telescope. Focusing of the collimator must be performed with the appropriate post-slit, order-sorting filter in place.