CelestronFocal Reducer & Field Corrector Imaging Accessory – Reduces Focal Length & Ratio 37% – f/10 to f/6.3 – Ideal for Deep-Sky Observing & Astroimaging – Works w/Schmidt-Cassegrain Telescopes

I am sorry that I did not buy this accessory two years ago. It all began with a used Celestron C5. Then I bought a very nice used Nexstar 8SE and thought wow, I should have done this go-to thing sooner. After a year or so, I moved up to a new Celestron CPC925 and decided to explore video astronomy with an inexpensive Samsung SBC-2000 security cam. Most SCTs have a focal ratio of about f/10 (focal length divided by aperture) but a camera works better with a faster (shorter focal length) scope. The usual way to do that with a video camera is to screw on a small .5x reducer. So I bought on of those for $35 and was just amazed at the detail and colors in the Dumbbell Nebula. Then someone over at Cloudynights.com suggested that try adding a f/6.3 reducer (stacking reducers). So I bought the f/6.3, screwed in on the back of the CPC925, replaced the visual back and diagonal, mounted the camera (without the .5x) and stayed up until 2AM looking at the Orion Nebula. Before heading for bed, I pulled the camera, put in a 20MM 68 degree APOV eyepiece, and had another "Wow!" moment.The Celestron f/6.3 reducer-corrector really brightens the image, widens the field of view, improves contrast and detail, and flattens the image improving the look of stars near the edge of the field of view. Many people leave them on all of the time except when looking at the moon and planets or other high magnification situation.There are other and cheaper reducers on the market and they do work. However not all of them offer the same degree of improvement at the edge of the field of view. Rod Mollise writes "...6.3 r/cs are one of the best--if not the best--SCT accessories to ever come down the pike" and "I'll put it this way...the 6.3 rarely comes off the rear cell of the C8."

Great product from Celestron and an imoirtant part of the image train on the Celestron 8SE AVX.

In perfect condition!

I read about such corrective lenses in a book on astrophotography. The goal of the lense is to effectively decrease the f value of your scope, increasing light gathering ability and the field of view. This lense accomplished both goals for my Celestron NexStar 6SE. It changed the scope from F10 to F6.3 and increased the FOV so that objects that formerly were too big to image "whole" now were imaged completely. The visual brightness of objects was increased and the resulting exposure times decreased. I keep this lense on the scope by default and only remove it (restoring the original F ratio) when intending to view and image planets or split close double stars. I have not noticed any distortion in the images when the lense is in place. I count this purchase as one of my best decisions when acquiring accessories.

My main motivation for buying this was to fit the sun (and moon) into the field of view of my APS-C (24 x 16 mm) camera sensor using my Celestron 8" SCT (2000 mm FL). Using a full frame sensor is not an option since the C8 will vignette. This device also allows a slightly wider field of view and lower f-number for deep space object astrophotography.Handy reference numbers for those wishing to photograph the Eclipse or just the entire moon: Max focal length when using an APS-C camera is about 1260 mm. When using a full frame, about 1900. But only if you can center the target and keep it centered. (To photograph the moment of eclipse use 400mm APS-C/600mm Full Frame and no solar filter.)This device is not useful for solar system astronomy, except the sun or moon, or when using eyepiece projection photography. But you can always just take it off.One huge advantage of this device is that you get just about the same performance as you would with an Edge HD telescope, and the field flattener costs half as much. If you buy an Edge HD 8" OTA you get a built-in field flattener, but still have the longer focal length, and hence smaller field of view and slower f-number. To see the whole sun or moon, or a more of the Pleiades in a camera, you would have to buy another focal length reducer, about $300 bucks. Since the Edge HD comes at a $400 buck premium over the SCT you spend an additional $700 bucks to get to the same optical setup you get with the the SCT plus this item at about $150 bucks. Go with this plus the SCT and save $550 bucks, and you will even have less glass between you and the stars to boot.The construction is very solid, you should have no problem hanging a DSLR (or better a mirrorless camera) off of this thing.

I put this on my celestron 8se SC telescope with the goal of increasing the field of view (because I have a zwo asi224mc camera with a relatively small sensor area). It was easy to install and worked quite well. Before buying it, I was worried that the focal plane would shift so much that I would not be able to focus within the limits of my focusing knob. But that worry was unfounded and I got to focus easily. I could fit the Dumbbell nebula with enough contextual background in the field of view of my camera. As far as I could tell, I did not observe significant vignetting. My plan is to leave it in the back of the telescope forever and only take it off when doing planetary observation or imaging (which requires higher magnification).

Mejora significativamente un Nexstar reduciendo su larga focal, haciéndolo más rápido en la captación de luz. Me gustó la calidad de su óptica. Me ha permitido mejorar las tomas y observación de objetos celestes de cielo profundo. La foto de la Nebulosa de Tarántula no es de gran calidad pero no es culpa del reductor focal. Ya sido una toma una toma con cámara planetaria. Aún lo estoy probando

This focal reducer turns my slow f/10 Celestron C-8 into a much faster f/6.3 telescope! It brightens and flattens the field significantly rendering stars sharp in the corners of my micro four thirds images. Highly recommended!