A focal reducer is part of optic whose main function is to enlarge the field of view of a refractor or a reflector and reduce the imaging time as well. It's very useful for SCT telescope like Meade LX200GPS series @ f/10.

The Meade f/3.3 CCD Focal Reducer/Field Flattener is specially designed for CCD imaging unlike the other type of FR such as Meade Series 4000 f6.3 Focal Reducer. In fact, the field illuminated by the f/3.3 image is so small that it can only be used for CCD imaging . Using it for photographic or visual observation will result in vignetting. This versatile part is included within a T-SCT adapter, 30mm or 15mm extension to offer different focal ratios as described in the table below.

Standard Telescope Focal Ratio	FR/FF with 30mm T-thread spacerreduction factor: 0.33	FR/FF with 15mm T-thread spacerreduction factor: 0.50
f/10 (Meade LX200 GPS Series)	f/3.3	f/5

As I already explained a few lines before, this optic part is dedicated to CCD imaging and particularly deep sky objects. In fact the main parts of Messier or NGC objects are too much large to be seen entirely in the CCD field of view. The other advantage of the FR remains in a larger field of view. Indeed, the tracking and guiding requirement can be less efficient, because imaging @ f/10 is critical. That's why the reduction of the focal ratio can help you to keep the target on the field of view during the imaging session.