With my C6 and a ZWO ASI294mc pro Bright stars produced rings like loops.
Celestron tech support have said this is caused by reflections within the baffle tube and it seems to effect some scopes and not others and is not a problem with larger scopes.
The suggested solution if the scope is out of warranty is to line the bafflevtube with flocking material to reduce internal reflections.
As the reducer and scope are both made by Celestron it is not really good!

Service from FLO was good as is normal from them.

Although the description says it is for 8" SCT it seems to work with 6".

Ive not had chance to use the reducer yet, but i have used one before its a must have for your SCT scope, as usually fast delivery from FLO
Tony

I bought this for my C9.25 which I use just for visual observing. It widens the field of view from 0.68 degrees (using a 40mm ep) to almost 1.6 degrees. This is wider than the maths suggests, but is confirmed as I can see both Gamma and Delta Coronis Borealis in the same field. The entire double cluster and coathanger asterism are visible for example. It also brightens the image without any discernable darkening at the edges. Stars right to the edge of the field are pin-point sharp.

On bright objects (moon and during the day), the central obstruction of the SCT is visible in the field at lower magnification, but that's a problem with physics and faster scopes, rather than anything wrong with the Focal Reducer. On other objects, including planets the OC isn't visible abd the view is delightful. (not that you'd really use this on planets).

A minor downside, as it changes the focal length of the scope considerably, there's a *lot* of focus changing when swapping it in and out. (A focus motor helps here). This is just a quibble.

I love this thing, it really does give the scope another dimension. All telescopes are a compromise, but with this in your toolkit you do kinda get the best of both worlds from your scope: wider fields for the DSOs and better magnifications for the planets.

I bought the Celestron f6.3 reducer with the hope that I could use it with a crayford SCT focuser. I was pleasantly surprised that it did. I'm really pleased with the product and really nicely made. First light optics was great to deal with as I'd read it couldn't be used with a crayford SCT focuser. Many thanks.

I tried the focal reducer with my C8 and i was amazed by the brightness and flatness of the imaged delivered. Perfect choice for any long FL SCT.