Haloes - where do they come from?

[pvelez]

I imaged Eta Carina last night for about an hour in LRGB - just as a test for my new set up. I have a new (to me) STL11000 matched with a Tak FSQ106.

I found that in the RGB data I have haloes around a few of the larger stars.

I'm interested in learning - where do they come from and how can they be avoided?

I know how to process them out in PI but it would be good to know how they come about so I can be more selective about my target or image strategy

Pete

[Geoff45]

Reflection from the glass cover of the ccd chip back up to the filter, then reflected back down onto the chip is the most common cause. Less common are dew on the OG, high thin cloud, dirty optics. Here is a comprehensive article http://www.astrodon.com/articles_faq/articles_faq/press_release:391,355,49
Geoff

[Octane]

That's odd.

What brand of filters?

I've never had any problem with my Baader 2" ones.

H