8 inch sct

[lesbehrens]

Hi, I have just got a 2nd hand celestron 8inch sct. I noticed last night observing the planets I noticed a half disc flare above the planet. Is this normal? I felt collimation was ok. Any ideas why I got this.
Thanks
Les

[Dave882]

Hi Les- the only time I’ve experienced this is when collimation was out or a tilt/flop in the image train. If you’re sure these are 100%, and after testing with different filters/camera/eyepiece to confirm none of these are affecting things it might be worth pulling the corrector plate off to ensure it’s centred and reference points line up. But only do this if you’ve exhausted other options and make sure you’ve read up on the correct procedure to do this first.

[lesbehrens]

I learnt how to do the collimation last night and used my best lenses. This seem to make the issue disappear. Thanks

[Dave882]

Good to hear. Hope you can get some clear sky while the planets are still nice and high!!