It is a high-quality made-in-japan focal extender lens for serious astrophotography. The Vixen Extender PH works with the optical surface of a parabolic mirror to correct coma aberrations on the Newtonian telescopes. It can transform an R200SS reflector into a research-grade F/5.6 astrograph with no false color, which is excellent characteristics of the Newtonian telescopes.
The Extender PH not only extends the focal length of the R200SS from 800mm to 1120mm (1.4 times) but also excellently corrects coma aberrations inherent in Newtonian reflectors.
The image circle of the Extender PH covers a full-frame DSLR with a 35mm image sensor format (36 mm × 24 mm). It achieves sharp star images throughout the photographic field of view.
The same anti-reflection AS coatings that are renowned for surprisingly high light transmission (99.9% per surface) on our high-end VSD100F3.8 are provided on each of the lens surfaces of the Extender PH. Besides, the matte-finish is elaborate to eliminate internal reflections and loss of light. Note: Use the R200SS together with a Wide photo adapter 60DX, and a Light baffle hood is recommended to get the most out of it.
The Extender PH can be fit on any of our R200SS reflectors sold in the past. If you possess the R200SS already, you will be able to change it into an F/5.6 astrograph of high performance with the Extender PH. It provids a wide illuminated field of view with no dimmer images at the edges of the field of view, and the coma correction is perfect throughout the image circle. It is available for visual observation with an addition of an eyepiece adapter.
The Extender PH works as a Barlow Lens by attaching to a 50.8mm visual back to the R200SS. You will obtain sharp images without coma in both visual observing and astrophotography. (The coma correction with this product is effective in any of parabolic mirrors theoretically.)