A curved focal surface is an inherent feature in most telescope designs. While this of no great consequence for general visual observation, for astrophotographers the consequences of that same curvature of field is a softening of focus in the outer parts of the frame. Designed for refracting telescopes, Explore Scientific’s Field Flattener does what its name implies; flattening a curved focal surface so that sharp focus is obtained over the full field.
This accessory sports fully multi-coated optics and slides securely into any 2” eyepiece holder. A gently tapered barrel section keeps the device from slipping out of the focuser if the locking screw loosens somewhat