Meade Series 4000 f 6.3 Focal Reducer Field Flattener (4-element 41mm dia.) for CCD, Photographic,...

Series 4000 f/6.3 Focal Reducer/Field Flattener: An important advancement in high-resolution focal reduction systems, the Meade 4-element, multi-coated f/6.3 Focal Reducer threads on to the rear cell of any Meade LX-Series mirror Focal lens telescope or to other Schmidt-Cassegrain telescope brands (followed by the Off-Axis Guider, shown, or T-Adapter) and reduces the telescope's focal ratio by a factor of 0.63: e.g., f/10 telescopes are converted to f/6.3. Simultaneously, the 41mm-diameter lens system helps to flatten the field, significantly improving edge-of-field corrections. The f/6.3 Focal Reducer enables a reduction of photographic exposure times by about 50%, while producing an actual field diameter of 1.5" at the film plane.

Reader Reviews
I purchase this Focal Reducer in order to take better pictures through my large-apperture Telescope (12 inches apperture). This is a great accesory in order to take better wide-field images of Nebulas, Galaxies, Clusters and the Moon with large Telescopes. I use it with my Canon Digital Rebel and my Meade DSI cameras.

You probably don't need this focal reducer if you have small apperture scopes (most refractors).