The Opticstar 1.25" Variable Imaging Focal Reducer will fit to any CS or C-mounted camera and has been designed solely for imaging. The focal reducer consists of a two lens cemented system for better correction, optics are fully broadband multi-coated. The two lens system sits is a metal cell that is threaded for filters.
The Opticstar imaging focal reducer can be used to reduce the focal length of the telescope in conjunction with an extension, i.e. 5mm C-rings. When used photographically the focal reduction will vary depending on the distance from focal reducer optics to the camera sensor.
The Opticstar variable Imaging Focal Reducer comes with three C-rings offering a focal reduction of F0.73, F0.66, F0.59 and F0.52 when used with a C-mount camera. Additional C-rings are optional. The three C-rings that come with the Opticstar Imaging Focal Reducer are CNC machined and nearly twice the weight of standard C-rings as used in the CCTV industry. High quality C-rings are desirable when stacked.
When attached to a telescope a f0.5 focal reducer will typically reduce exposure times to near a quarter when imaging extended objects like galaxies, nebulae and the Moon. Telescopes with low focal ratios require shorter exposures when imaging extended objects (for example an f/8 system will require four times the exposure of an f/4 system). This does not apply to non extended objects (point sources) like stars where aperture dictates what can be seen/captured.