At present, we have 31 narrow band filters, mostly of 50Å bandwidth,
comprising a set of emission line filters and a set of redshifted H
redshifted filters. Only one set exists and therefore the filters are shared
between the telescopes.
These filters were specified for a focal ratio of 4.5 which explains
the difference in wavelength between the actual peak wavelength and the
required peak wavelength. The original specification for the emission
line filters is given below: