A stable light flasher (perhaps with monitor) can be used with a trusted light sensor to measure the filter transmittance, mirror reflectivity, and the cluster PMT responses to a known intensity light source positioned at the mirror center, for example.
(A stable light flasher; can be used; to measure the filter transmittance, mirror reflectivity, and the cluster) (the cluster; responses; to a known intensity light source) (a known intensity light source; positioned; at the mirror center, for example)
A stable light flasher the cluster a known intensity light source
can be used responses positioned
to measure the filter transmittance, mirror reflectivity, and the cluster
to a known intensity light source
at the mirror center, for example