Properties of the instrument that are associated with the instrument as a
whole, rather than with a particular filter or detector channel, belong in
descriptors in the instrument table file.
Most of these relate to the filter mechanisms.
In addition, it is convenient to have a character*72 descriptor
called INSTNAM that gives
the name or designation of the particular instrument; and one to describe the
condition of the telescope optics, which will be treated at the end of this
section.
The descriptors are summarized in Table 
.