Starizona Apex ED 0.65x Reducer / Flattener


Item Description

Reduction Factor

Image Circle


Optical Design

Barrel Diameter

Camera Thread

Filter Thread

Overall Length (Apex ED L)

Weight (Apex ED L)

Overall Length (Apex ED S)

Weight (Apex ED S)

Starizona Apex ED 0.65x Reducer / Flattener

0.65 x

30 mm

55-62 mm (depending on telescope focal length)

5 elements with ED glass, fully multi-coated


M42 (T-thread)

M48 (2" filter)


318 gr (0.7 lbs)


327 gr (0.7 lbs)


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.





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.




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.

Apex ED S

Apex ED L

Telescope Focal Length

500 - 600 mm

600 - 700 mm

700 - 900 mm

> 900 mm


58 mm

57 mm

56 mm

55 mm

Telescope Focal Length

< 350 mm

350 - 450 mm

450 - 500 mm


62 mm

60 mm

59 mm

Backfocus example with common imaging set-up

Esprit 100 + Apex ED L + ZWO ASI 1600

58 mm Backfocus

                                                                                                                                 M48-T2 16.5 mm extender                             11 mm ring                                T2 - T2 adapter                                   EFW/EFW mini                                Cooled Camera

                                                     48 mm Threader Adapter                          (Comes with camera)                           (Comes with camera)                  (Comes with EFW)                                                                                         (without 11 mm ring)

                                                  (Comes with two 1 mm spacers)

                                                          1 mm                             1 mm                                         16.5 mm                                           11 mm                                               2 mm                                                    20 mm                                                    6.5 mm


Reducers / Field Flatteners