Meade - Series 4000 f/6.3 Focal Reducer/Field Flattener
The Meade 4-element, multi-coated f/6.3 Focal Reducer threads on to the rear cell of any Meade LX-series mirror-lens telescope or to other SCT brands and reduces the telescope's focal ratio by a factor of 0.63: f/10 telescopes are converted to f/6.3; f/6.3 telescopes to f/4 and f8 RCX's to f5.
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 in photographic exposure times by about 50%, while producing an actual field diameter of 38mm (1.5") at the film plane.
Essential for DSLR astrophotography