Celestron Reducer/Corrector f/6.3 - 94175

Haven’t really had a chance to fully utilize it 100% but seems to work well

I installed the Celestron F6.3 reducer/corrector onto a Celestron 9.25" Evolution at the recommended back-focus of 105mm. Here's what I found...

What I Like
- Excellent build quality.
- Good optical quality yields sharp image corners and edges.
- Very easy installation. Whole unit threads directly onto the telescope's rear cell.
- Back-spacing is quite forgiving meaning mounting it short or long by 5-10mm still results close to F6.3. At 105mm the reduction is the advertised F6.3.

What I Don't Like
- Too expensive
- At the recommended 105mm backspacing and with a camera installed, you won't be able to reach more than about 65 degrees elevation using a balanced tube. To reach 90 degrees you'll have to move the OTA close to the end of its mounting rail putting the OTA well off balance, which is what I did. The 'scope doesn't seem to mind being well off balance as my Go-To’s and tracking remain very accurate. Or, you could use a 90-degree diagonal and keep the ‘scope balanced (but I don’t like the mirror-reversed image).
- When installed the focal reducer results in views/images that have A LOT OF VIGNETTING. Visually this is annoying, especially in my light-polluted sky where the field of view is bright. For imaging, the solution is to take and use "flats". This fixes the vignetting but it also means the now looking normal corners have lost quite a bit of light sensitivity. However, your imaging targets generally occupy the center of the field so this isn’t usually a problem.

Bottom Line
Though over-priced this FR is a good addition for this telescope because imaging without it results in my camera "oversampling" the target. The FR fixes that but flats must then be used and the OTA must also be relocated forward or a diagonal used instead. So we have a situation here where the solution generates other issues which also must be addressed. That’s a negative. But it still works for me.