This is the internal filter wheel for the SBIG STF-402M only. It contains very high quality interference filters custom made for this camera. Note that the filters are permanently attached to the filter carousel and cannot be changed.
An internal filter wheel with custom RGB+C color filters is available as an option for color imaging with the STF-402M. The filters are designed specifically to yield a proper balance of both OIII and H-alpha emission line intensity from planetary nebula while at the same time giving an accurate while balance from continuum light from solar type stars in the same field.