This revolutionary new William Optics AFR-IV Adjustable Flattener and (0.75x-0.8x reducer) was made for 500-1000mm refractors.
Super-Transmission-Coated with 2-element unit was designed and produced by William Optics, the inner flattener lenses can be set at the optimum 66mm-86mm back focus by simple hand twist (Distance from flattener lens to film or CCD plane).
This accessory is a must-have for refractor astrophotography.
Lens:
- Designed to cover full size DSLR cameras with clear lens aperture of 50mm.
- STM coated with excellent doublet air spaced design.
- Produced entirely with the best Ohara optical glasses.
- 35mm for full illuminated imaging circle.
Amazing:
- It will flatten the field amazingly well and finally make you see those stars round!
- This unique flattener/reducer works with William Optics or other 500-1000mm focal length refractors.
Superb:
- Superb William Optics anodized finish.
- All internal surfaces threaded and blackened for no reflections.
Easy to use:
- Rotating T-ring thread for any 35mm camera. The T-ring adapter is provided with a lock screw and extra lock retaining screws.
- Will accept any standard T-ring for your camera.
- Inserts directly into 2" focuser.
Our expert comment:
The distance between the thread of the flattener and the camera chip should be between 66 and 86mm; an average value around 76mm would be ideal because then there is still room for fine adjustment. The flange focal distance of the cameras can be found in Wikipedia under the keyword "flange focal distance". If, for example, an EOS with a flange focal distance of 44mm is to be used and the T2 ring is 9mm thick, a distance of approx. 23mm is required.
Suitable extension rings are available here:
and here:
(Bernd Gährken)
