New G4 camera adapter for ASA Wynne coma-corrector

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No optical setup is capable to cover really wide field of view without refracting correction elements. Even the best and most expensive APO refractors and RC reflectors need field-flatteners if a 50 mm diameter field has to be utilized. With a little exaggeration, spending money for premium optics, which must be corrected either way, is not necessary when much cheaper optics with a quality corrector provide the same results. And in reality well corrected Newtonian reflectors proved to be the best wide-filed, large-diameter telescopes available to amateurs. The trick is in the refracting correction element just in front of the camera, which eliminates the so-called “coma” aberration, inherent to simple parabolic mirrors. And the 3" Wynne coma correctors belong among the best available.

The 3" Wynne coma-corrector is capable to cover the 36 × 36 mm sensor of the G4 camera with pinpoint star images. Also vignetting is acceptable if slower than f/4 primary (and appropriately big secondary) Newtonian mirror is used. Unfortunately the mechanical design of the corrector provided by ASA brings some challenges when the corrector has to be attached to the camera and possibly the OAG. The corrector tube has to be attached using six M3 screws from the camera side. A question how is it possible to screw in some screws from the side of camera when a camera must be there naturally arises.

The 3" Wynne corrector also requires back focal distance between 58 and 59 mm. It is necessary to stack a sensor in the insulated CCD cold chamber, mechanical shutter, filter wheel for reasonably thick filters and OAG into this space and also provide necessary room for screws holding the corrector.

The 3" ASA Wynne coma corrector adapter on the G4 camera body

So we designed ASA 3" Wynne adapter for G4 cameras consisting of two parts. One part replaces the M68 × 1 threaded ring on the OAG (the Wynne adapter itself does not use the M68 thread). The other part is attached to the Wynne coma corrector using six M3 screws. The another set of six M3 screws is used to hold these two parts together.

The 3" ASA Wynne coma corrector adapter on the G4 camera body

Remark:

Please note the adapter is intended for G4 OAG only. The mechanical diameter of the 3" ASA Wynne corrector flange does not allow the usage with G3 cameras, as the G3 OAG places the guiding camera port closer to the optical axis so it interferes with the corrector body.