The flattener is a lens that evens out the field, as this is slightly curved by the primary optics. This curvature causes stars that are imaged at the edge of the field of view to be less sharp. The flattener, also called a field flattener, corrects this effect. Astrophotographers can then enjoy images where the stars remain sharp right out to the edge of the exposure. The flattener is installed between the telescope and the camera.
The Reducer (for focal length reduction) is an optical accessory that allows a more favourable aperture ratio. Required exposure times are hence shorter and the optics 'faster'. Also, the field of view increases, so that even larger astronomical objects can be observed or photographed.
This flattener/reducer is ideal for refractors with a 105 to 120 mm aperture and an aperture ratio of f/7 to f/7.5 when using a DSLR camera in APS-C format. The required back focus of 55 millimetres is already achieved with this type of camera by the optional T2 ring, which is used to connect the camera to the flattener. The corrected image field is large enough for the APS-C format.
The flattener can be easily connected to the telescope via the 2" barrel. A 2" filter can also be screwed into the barrel.
The 0.8x focal length reduction reduces the exposure time to 64%.
