An inexpensive internal filter wheel for the ST-402ME for photometric work using the B, V, I filters of the common UBVRI filter set used by professionals. Normal UBVRI filters cannot be installed on the ST-402 internal carousel. Note that the filters are premanently attached to the filter carousel and cannot be changed. Also, due to the size of the CCDs, the internal filters will not cover the KAF-1603ME or KAF-3200ME CCDs. For the larger ST-1603ME and ST-3200ME cameras, the external CFW10 filter wheel must be used.