Custom Scientific Photometric Filters
UBVRI Photometric Filters
Custom Scientific makes filters and other optical components for research and amateur astronomy. Many of the larger filters made by Custom Scientific are one of a kind filters made to the specifications of a particular user. Custom Scientific UVBRI filters are used world wide by researchers in the field of photometry.
In the 1950's Harold Johnson (Yerkes and Macdonald Observatories) established three photometric bands, the U, B, and V based on the sensitivity of the photomultiplier tube that he used at the time. Later on he established red and infrared (R and I) bands using a PMT with enhanced red sensitivity. In the mid-1970's, A.W.J. Cousins and John Menzies (South African Astronomical Observatory) used different filters, that when used with a newer, better detector, would reproduce the Johnson bands. Then, in the 1980's CCD detectors were beginning to replace the photomultipliers so a new set of filters was required that, when used with the CCD's would give the same results as the older filters when used with the PMT. Bessell (Mt. Stromlo and Siding Spring Observatories in Australia) did this in 1990 (PASP, 102, 1990, 1181). It is Bessell's filter definitions that are the industry standard today when using CCD's. These professional quality, polished, AR coated, photometric filters are available in various standard sizes as well as a custom size for the ST-402ME camera.