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.
Designed specifically for the Sky-Watcher Esprit Apo Refractor, the new three-lens Focal Reducer/Flattener has a reduction factor of 0.77x. It comes with a standard adaptor with M48 thread edge and 55mm back focus for use with Sky-Watcher's M48 Canon EOS and Nikon adaptor rings. After removing the adaptor, an M71x1 internal thread with maximum 75mm back focus is available for self-made adaptor solutions.
The Reducer/Flattener produces a fully illuminated and corrected image circle of 36mm diameter and is therefore perfectly suitable for image formats up to APS-C but can also be used for full format.
