As a high-powered stargazing tool, this 0.77 Reducer / Flattener from Sky-Watcher is a must-have for astrophotographers utilising the Esprit-150ED Professional Super APO Triplet Refractor OTA. In short, the field flattener accurately corrects the inherent spherical aberration of curved lenses. Without such a tool, image quality is lessened as the frame appears distorted at the edges of the field of view. When used as a focal reducer, you are afforded a key reduction in the focal ratio of the scope. By doing so, you are left with a wider field of view with shortened exposure time, allowing for more images to be captured in a shorter amount of time without affecting their overall quality.