Quick n dirty M45 - 3x1200 no CLS - why a halo?

[Tim]

I was disappointed with the images I got at Kelling because of a large halo effect around the brighter stars. I assumed this was caused by my CLS filter in front of the IR/UV nosepiece in the QHY8. So last night I dropped the filter and ran this test image. Got a nice orange sky of course, but PI got rid of that.

There is still a large halo around Alcyone though. Is this likely to be caused by the glass of the refractor, the reducer, or be an artifact from the IR/UV filter???

On the plus side, it's the first time I have been able to get any decent amount of the reflection neb around M45 from home, the Borg has helped with that I think, and the long subs too.

Borg 77EDII > DGL 0.85 reducer > QHY8 - 3x1200secs >DSS>Pixinsight (levels, DBE, ABE, curves)

Crop of alcyone superstretched included to highlight the issue.

Cheers

TJ

[Steve 1962]

Hi TJ

That's a coincidence - I've just sat all evening looking similar halos around the same star - I've posted the image here - do we have identical problems or is it atmospheric?

http://stargazerslounge.com/imaging-deep-sky/116177-m45-pliades.html

Cheers

Steve

[MartinB]

Not sure what's causing it but guess it is dew somewhere. The good old QHY8, I've spent the last night and a half doing battle with mine, lots of ice on the chip.

[brianb]

Not sure what's causing it but guess it is dew somewhere.

Or a very thin layer of uniform high cloud (cirrostratus) which you probably wouldn't be aware of ...

[Tim]

That sounds more likely than dew Brian. I'll try the same thing again over a few nights, same exposure same setup and see if it varies.