The Sky-Watcher 0.77x Flattener/Reducer for Esprit 150ED telescopes shortens the focal ratio of the 150ED to f/5.4 and focal length to 810mm. Exposure time is reduced by 68% when compared to the native f/7 configuration.
The illuminated and corrected image circle is 36mm, making it suitable for use with APS-C sensors and smaller.
The flattener/reducer has a back focus requirement of 90mm (55mm when paired with the included spacer and M48 adapter), making it possible to connect a wide range of imaging trains. Built-in 2" filter threads allow you to add light pollution filters with ease.