Halo issue

[DiscoDuck (Paul)]

A newbie question ... but in the attached image (quick stretch of stack, so please excuse the rubbish quality!!) of a portion of M42 (trying to build a mosaic), there's a strong halo down the left hand side. Presumably from something like Alnitak (though quite a way away)??

Do other people get such effects? Is this due to some atmospheric peculiarity, as it wasn't visible in the same area in an overlapping image taken another night?

Anything I can do to mitigate? (Just simply Photoshopped it out in the mosaic so far! http://astrob.in/232769/0/)

Paul

P.S. Was present in all frames across a 4 hour period, so wasn't some local light source.

P.P.S. And that bright patch in the top right is a concern too! Though I should handle one issue at a time I guess

[glend (Glen)]

Could be a light leak. What camera are you using? What were the circumstances of the shot, was it inside an observatory, outside on a tripod, any light sources nearby, etc?

[RickS (Rick)]

It's common for very bright stars outside the FOV to leak into it but that usually shows up as a gradient or rays pointing towards the star. An arc like that is probably a reflection off something shiny in the imaging train. Take a careful look for anything that isn't blackened.

Cheers,
Rick.

[DiscoDuck (Paul)]

Originally Posted by glend

Could be a light leak. What camera are you using? What were the circumstances of the shot, was it inside an observatory, outside on a tripod, any light sources nearby, etc?

Sorry. Should've given more info. It's a QHY8 and running outside on a tripod. No significant light sources nearby ... and given the location of the halo is the same in all frames across 4 hours then I'd guess it couldn't be a nearby light source.

I'll check for light leaks. Thanks for that suggestion.

EDIT: Just thought, the dark frames don't have a halo, so presumably this suggests no light leak??

Originally Posted by RickS

It's common for very bright stars outside the FOV to leak into it but that usually shows up as a gradient or rays pointing towards the star. An arc like that is probably a reflection off something shiny in the imaging train. Take a careful look for anything that isn't blackened.
.

Hmm. Thanks for that info. That helps narrow it down. Will have a peer around inside.

[Paul Haese]

Its the primary baffle tube on the RC8. How old is the telescope? If it is a second hand or older scope, you will need to get the baffle tube extension from a supplier. Or you can remove the baffle and line it with a black felt from Spotlight. That is what I did to get rid of the problem. It was a problem in the original RC8's but was subsequently fixed with properly baffle edges and a slightly longer baffle.

[Paul Haese]

BTW that mosaic is coming along nicely.

[PRejto (Peter)]

I think there could be something else going on. I've noticed that the amount of moisture in the atmosphere from night to night can cause flares to appear where before there were none. Think of how the moon looks on wet nights...there is often a large ring of brighter sky not seen on dry nights. So, maybe??

Peter

[DiscoDuck (Paul)]

Originally Posted by Paul Haese

Its the primary baffle tube on the RC8. How old is the telescope?

Thanks for the info Paul. I picked it up in 2012, but second hand. Not sure how old it is then. But at least 3 and half years, so it's probably in need of that fix. Thanks again.

Originally Posted by Paul Haese

BTW that mosaic is coming along nicely.

Thanks

Originally Posted by PRejto

I've noticed that the amount of moisture in the atmosphere from night to night can cause flares to appear where before there were none.

Thanks for that Peter. I certainly haven't experienced it before, I must admit, in 3 years of imaging. Hoping it's rare then.