This field flattener is suitable for most doublets and triplets from f/5 to f/9. Please see the back focus chart for recommended spacing for given focal lengths. The flattener has a male M68 thread and will attach to any focuser that uses a female M68 thread. Adapters can be used for other thread sizes. SharpStar have designed this flattener with a long back focus distance to facilitate the use of accessories such as Off Axis Guiders, Filter Wheels etc. Specifications Field flattener for f/5 - f/9 refractorsFull aperture: 61.5mmThread on camera side: M69 femaleThreads on telescope side: M68 male and M63 femaleFully multi-coated optical surfacesBlackened interior for improved reflection suppressionRecommended distance between camera side thread and focal plane: 91.5mmM48 adapter with 36.5mm length included (to create 55mm back focus from adapter to camera sensor)Overall Length: 79.7mm
