The 50ED Flattener from Sky-Watcher is designed to allow for both the Evoguide 50ED and 50DX telescopes to be used for astrophotography because it will correct for field curvature. It is equipped with thread-on metal caps, a T-thread connection or 1.25" opening for camera mounting, and 17.5 mm back focus. This flattener has a 5.33 x 3.57-degree field of view when it is used with an APS-C crop sensor and a 28 mm imaging circle.