Is this ice on the CCD?

Hi guys,

The QHY6 arrived yesterday and lo & behold we had a clear night. I managed to get about 10 shots of 120 seconds with an IDAS lps filter before the camera went crazy but looking back at the light frames I see these weird "branches" at the edge of the field. There was alot of dew last night & it was quite cold so I'm wondering if the cooling caused ice to form on the CCD.

I'm not worried about the severe vignetting as I think that was caused by my using a flip mirror in addition to the filter wheel - I'll take that out of the optical train the next time I image.

Anyway, here is a single frame that I pushed the levels way up on to show the effect at the edge of the frame. Any idea if this really is ice? If so what do you normally do to combat this - just turn off the peltier cooling or add silica gel?

I'm going to post this to the QHY forums as well but I guess it will be a few days before the moderator is online to approve my membership.



I'm hoping this is the problem rather than an issue with the camera itself because from around subframe 15 I got effects like this - although it looks more like a usb tx corruption.





Many thanks,

Trev

Hi Trevor

It is more likely to be caused by dew forming somewhere n the optical train itself. I think only a small amount of dew is sufficient to give this result. I had almost the exact same images in a particularly dew filled night in Birr a few years ago. It has not happened again to the same extent since even on nights that were much colder.

Hope this helps.


DB

The glow could be dew like Dave says.
I've never seen the fingers before, would ice not form in the center of the fov and work its way out to the edges.?
I used a st4 guider and added silica into the ccd compartment and it helped prevent internal ice issues, also watch out for dew on the filters.

Thanks guys, just the information I needed.
It could be that dew got onto one of the filters. I'll need to keep an eye out the next time I image.

Trev