The Copper Sulfate Crystal Filter - Precautions
Blue copper sulfate has some of the best red-blocking properties of any
known substance. This crystal filter is a mosaic of three pieces of crystal
mounted between two quartz cover windows. Some precautions to using this
The filter is very fragile and should not be removed from the filter slide.
Due its rectangular clear aperture, the filter should not be used for multislit
observations (which require a round clear aperture).
Due it its construction, the filter is particularly sensitive to shearing
by temperature variations. Do not take this filter from the cold dome into
the warm control room.