Introducing Starizona's 5-Element Apex ED 0.65x Reducer/Flattener for Apo Refractors and RC/ACF Telecopes. This focal reducer was designed for apo refractors used by many astrophotographers. It will also work on Ritchey-Chretien (RC) and Meade ACF telescopes. The reducer provides a 0.65x reduction factor and produces pinpoint star images by correcting for the field curvature and astigmatism present in standard apo doublets and triplets and RC/ACF telescopes.

 

 

Vignetting issues in flattener/reducer systems

 

The vignetting is perfectly normal.  When optical designs state an image circle, that means that the stars are corrected and sharp over that circle, but it does not mean that circle is fully illuminated.  That is almost never the case with any optical system.  Pretty much all focal reducers on any scope will show vignetting.  The Apex will show some vignetting but proper flat field images will perfectly remove it.  Be sure to take bias frames or flat darks along with the flats in order to properly calibrate them.  But that will do the trick!

 

 

DETAILS

 

With the Apex ED reducer, an f/5.5 apo refractor becomes an incredibly fast f/3.6 astrograph. A slower f/9 telescope like an RC becomes a speedy f/5.9 system. The reduction factor provides a 1.5x wider field of view and shortens exposure times by a factor of 2.4x!

 

The Apex ED reducer features extra-low disperion glass to eliminate chromatic aberration and to provide sharp star images over a 30mm image circle, capable of working with most popular CCD, CMOS and DSLR cameras up to APS-C format.

 

The Apex ED reducer fits into a standard 2" focuser. It has M42 T-threads on the camera side, and it can accept a standard 2" (M48) filter on the telescope side for easy use of light-pollution or other filters. On Meade ACF telescopes, the Apex can be attached using a 2" visual back.

 

For select refractors, we make optional threaded adapters to allow direct threaded attachment of the Apex reducer, eliminating the possibility of tilt introduced by the standard focuser clamp ring.

 

"L" and "S" Versions

 

To optimize the Apex ED for the best possible performance, there are two versions of the lens. The "L" version is designed for telescopes with focal lengths 500mm and longer. This includes most larger (100mm+) refractors and all RC and ACF telescopes. The "S" version is for telescopes with focal lengths from 300-500mm, including most 60-80mm apo refractors.

 

Backfocus

 

The nominal backfocus distance from the Apex ED reducer's T-threads to the image sensor depends slightly on the focal length of the telescope. It is at least 55mm in all configurations. The table below shows the optimum backfocus for various focal lengths. Please contact us for help in choosing the right adapters or spacers necessary for your setup.