Meade - Series 4000 f/3.3 Focal Reducer/Field Flattener with Variable T-Adapter
The CCD Focal Reducer converts the optical systems of f/10 STCs to f/3.3, or f/6.3 SCTs to f/2, f8 RCX's to f2.6 for ultra-fast CCD imaging with increased edge of field resolution and colour correction.
Mounted in its threaded cell, the f/3.3 CCD Focal Reducer attaches to the rear cells of all Meade LX-Series Schmidt-Cassegrains and to other SCT brands and reduces CCD exposure times by up to 80%.
The 3-element, 41mm clear-aperture optics are multi-coated to maximise light transmission.
Included with each f/3.3 CCD Focal Reducer is a Variable T-Adapter (that comes with 15mm and 30mm spacer tubes) that allows a range of f/ratios between f/3 and f/5 on f/10 SCTs and between f/1.9 and f/3.2 on f/6.3 SCTs. For example, on a f/10 SCT:
Using the 15mm spacer gives about a 0.5 reduction.
Using the 30mm tube gives a 0.33 reduction.
Using both (15mm+30mm) gives about a 0.3 reduction (but this setup doesn't work with all configurations).
The Focal Reducer may be used with CCD imagers of any brand and chip dimension but is not recommended for use in either visual or photographic imaging applications.
Essential for wide-field astrophotograpy