Explore Scientific's 3-inch Field Flattener/0.7x Focal Reducer is a multi-faceted accessory designed to enhance your astrophotography experiences. As a field flattener, this piece addresses the edge-of-field aberrations caused by curved focal planes to ensure your night at the eyepiece will result in crisp, true images.
As a focal reducer, this device will reduce your f-ratio by 0.7, which results in a wider field of view, brighter images and less exposure time. Recommended for our 127mm and 152mm refracting telescopes (excluding our doublet refractors), this field flattener/focal reducer boasts fully multi-coated optics.
This item comes with a threaded adapter that threads onto the Explore Scientific 2-inch rack-and-pinion focuser. Threaded attachment to a 2.5-hex focuser, which comes stock on Explore 102mm and 127mm APO telescopes, requires purchase of an additional adapter: Explore Scientific Adapter FFFR507X-00 to 2.5" Hex Focuser - 510366.
The field flattener/focal reducer offers 55 mm of back focus from the rear flange. The M42x0.75 adapter is 6.25 mm thick with a working length of 1.8 mm.
While technically this was designed for the f/8 system, through user experiences and our subsequent testing we have concluded that our 3-inch field flattener/reducer performs very well with our f/7.5 refractors.
The camera side connection is M42. The flattener also comes with an M54 adapter, giving you a female M54 connection.