Any ideas...

...as to what might be causing this? It's a 15 year old SBIG 2000 camera and it does it with all filters, the sensor looks clean.

Single 120s frame.

Thanks,

Keith

Attached Image:

Frost? But it doesn't look quite like frost that I've seen before. Is the cooler on? Does it change when the cooling is on/off?

Here is my 2 cents. I have a ST8-XME that experienced something similar. Bottom line, turned out to be frosting. Try this: take an initial pic as a reference then let the camera run for an hour or so before trying to take another pic. If that pattern has disappeared, more than likely frosting. Now how to correct. Bake or replace the desiccant and see if that helps. In my case, I had the camera in for repair and Bill (at SBIG) replaced some seal that he said was marginal that probably contributed to the frosting. Got the camera back, baked the desiccant and that pattern disappeared. Hopefully you can get by with replacing the desiccant.

Chris N
Cedar, MN