This large format field flattener is designed to work with the Altair Astro 102mm, 115mm and 130mm F7 EDT Triplet APOs, and has an M48 rear conical adapter for connecting your DSLR or CCD camera.
It is compatible with 35mm format CCD chips, utilising about 95% of the field. The flattener works best at F7 with about a half F stop tolerance. The flattener screws into the rear focuser rotator of your Altair EDT APO, converting it into an astrograph with a flatter photographic field.