SCT 8" reducer problems

[vigsoe]

I have just recently bought a Celestron 0,63 reducer for my Celestron 8" SCT - and I get some weird artefacts when using it - please see attached pdf.

Any of you out there experienced something like it? Do any of you have a solution for it?Reducer artefacts.pdf

[redfox1971]

HI that's caused by the bright star at the edge of the sensor not a lot you can do except maybe flock the inside of the baffle tube and scope by that i mean line it with dark material available from first light optics.its the reducer reflecting the light back into the scope.

Edited April 7, 2020 by redfox1971

[Louis D]

I get almost the exact same artifact using widest field 2" eyepieces with my 127mm Mak.  The artifact first manifests itself as the star crosses the edge of the rear aperture/baffle tube (27mm diameter) and grows bigger as the bright star is brought closer to the 46mm diameter field stop.  I'm sure it's a narrow angle reflection off of some blackened internal surface in the rear baffle tube.  As such, it would probably take a knife-edge baffle somewhere to reduce it.

Since your rear baffle is larger at 37mm, the effect is probably not visible without the focal reducer unless you were to use a larger format sensor.  Try looking through the focal reducer with a 32mm Plossl to see if you can replicate the effect visually.  That would eliminate the camera as the cause.  See if you can see it visually with a 2" eyepiece having a 40mm to 46mm field stop with a 2" visual back and no focal reducer, or just hold the eyepiece up to the open back of the tube if you don't have one.  That would eliminate the focal reducer as the cause.

[vigsoe]

Thank you for your answers "redfox1971" and "Louis D". I also have an on-going discussion with Celestron support - the above is good input 🙂 I will be trying to use an eyepiece ... thanks again!