Starizona ApexED-L 0.65x Reducer/Flattener - long focal length Version

Starizona ApexED-L 0.65x Reducer/Flattener

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-Chrétien (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.

Optical benefits:

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 dispersion glass to eliminate chromatic aberration and to provide sharp star images over a 30 mm image circle, capable of working with most popular CCD, CMOS and DSLR cameras up to APS-C format.

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

The mechanical connection:

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. We recommend to use a threaded connection if possible, as it reduces the risk of tilting. Adapters for most telescopes ara available from Teleskop-Service.

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 55 mm in all configurations. The table below shows the optimum backfocus for various focal lengths:

Video presentation:

An iteresting video about using the ApexED reducer can be found on YouTube.

A concrete example using the ZWO ASI533MC Pro can be found here on YouTube.

Question:
How do you have to measure the working distance?

Answer from Teleskop-Service:
The working distance is measured from the beginning of the connection thread on the housing of the corrector (see example picture):