Image oddities

[Lee_P]

Hi all,

Last night was the first chance I had to play with my new toy, an i-Nova NBB-Cx camera. Attached is a test shot of Comet Lovejoy. Any idea what's causing the bright glow to the top-right of it? It's visible in many pictures, so I suspect it's sensor related. Also, I thought the stars were in focus but they're blurry around the edges. Any thoughts on why? This particular shot was a 2-minute exposure, and the sensor itself was at around -41 degrees C, if the software was telling the truth!

This was my first night having graduated from DSLR imaging, so sorry if there are obvious explanations to these questions...

[Davey-T]

Moon ?

Dave

[Thalestris24]

Dew? And/or light pollution?

[Lee_P]

I don't think it's any of those things. I've just been taking new snaps around the sky, and that lighter blob is present in the same place on all the pictures. So it can't be dew as I've only just set the 'scope up; can't be the Moon because it's cloudy at the moment (!); and can't be light pollution because it's in the same place even when the telescope is pointing in different places.

[Davey-T]

Is it still there if you take flats ?

Dave

[Lee_P]

This was one of the flats I used. I can't see it on there. Maybe the settings used weren't the best?

[Lee_P]

Here's another clue: a strange halo around a bright star.

[zcdawson]

Reflection?

[Thalestris24]

Hi again

Having read the op again, I reckon it's an ice problem at the camera end.

Louise

Edit: or dew/condensation at the camera end

[Lee_P]

Thanks for all the replies. After packing down I removed the camera to check the sensor and it was dripping with dew, so that must have been the cause. Is it to be expected that dew would cause a patch of light in the same shape and position over different nights? And it must have dewed up really quickly - especially as the telescope and finder lenses were fine. A consequence of the camera being cooled? And suggestions for limiting the problem?

[Thalestris24]

Hi Lee

Maybe you can do something to limit the cooling? Perhaps keep it to -10 or even just -5?

Louise

[Lee_P]

There doesn't seem to be any option in the software to change the temperature, unfortunately. I could disconnect power to the cooling, but then there's not much point in having it! 

[Davey-T]

Strange it doesn't have set point cooling, pretty well expected for an imaging camera nowadays unless it's a video camera, does the software come with the camera ?

Dave

Just read the blurb on it, so no set point cooling which is strange as they say it can be used for imaging DSOs and stacking them for which you'd want darks at the same temp' not much good if you can't control it.

[Thalestris24]

Hi Lee

Possibly fit a power controller (such as used by dew controllers)? Perhaps have a word with the camera manufacturers. Does it give any guidance in the manual? Is there a users group / forum? Presumably other users have had the same problem.

Louise

[Lee_P]

I've e-mailed the manufacturers to see if they have any suggestions, and will update this thread once I have a reply in case it's useful to anyone else.