Any-one know what's going on here?

[Carole]

I know not many people use newtonian's here but hopefully those that do might be able to help.

I went out the other evening with my Atik, and Newtonian to capture Leo luminance with a plan to add it to my DSLR data already collected.

Firstly I cannot get the right spacing with the coma corrector as there is nothing I can remove to reduce the distance. 

Ideal spacing for 200PDS with CC is 55mm so I have been told
Atik 383L sensor to front of camera 17mm
Filterwheel 25mm
CC 17mm with no spacers added
Total 60mm
(5mm too large)
Have I got any figures wrong here?  

However this is not the major problem that concerns me, it is the results of the image as attached. Huge spot in the middle and swirls around M66. Gets even worse if I stretch it.

All new dessicant and kept in a sealed box with more dessicant.  However some-one told me that camera glass in front of the sensor can be prone to frosting up with Newtonian's being open to the night air and it was jolly cold that night.  



This is what the Master flat looks like and I have stacked it in both DSS and Nebulosity with the same result. Any ideas what is going on? What's that huge bright blob in the middle, I guess it probably has a lump of dust as a bite into it.

It's almost as if the flats are doing the damage, but I've tried it without flats and that is just as bad if not worse.
Thanks Carole

[Mike]

Looks like a classic case of condensation to me.

Do you have condensation inside the CCD glass somehow? I've seen that before when seals have failed.

[Carole]

Do you have condensation inside the CCD glass somehow?

Don't think so Mike. I think it's more likely frosting.  But as I wanted to do flats the next morning, the camera had to be left on overnight so I wasn't able to prove it.

Carole

[Fay]

perhaps that is the problem, Carole, leaving the camera on over night.

[Carole]

Fay I have a dehumidifier in the obsy and have always left camera on overnight to do flats and not had a problem before even with the newtonian.  The artifacts are also on the subs anyway done at the time.

As I say it all worked OK with the DSLR on the Newtonian, some people are suggesting reflections, but I would have thought I'd have got it with the DSLR if that was the case.

Carole

[Mike]

The dehumidifier may well not be removing the moisture as quick as it is condensing inside the observatory.

[Carole]

Mike I was thinking maybe it could be condensation getting on the filter.

Carole