Below is a screen capture from some images this summer. I think it’s dew forming and not ice but a second opinion would be great. Please advise, this is two STL-110002M frames taken using my OGS 12.5”RC with the three telescope fans turned on, dew heaters running, and imaged at -15C. http://www.astral-imaging.com/DeworIce.html My thoughts are this is dew forming on the secondary mirror but it’s just a guess. The telescope is a carbon fiber tube, not open truss. Thanks, Steve
Steve: It looks like that might be ice forming on the inside of the window. I see this frequently when the weather/humidity is very high (i.e. rain). Try turning the camera on about 30-60 minutes before imaging with the cooler off or at 0 degrees. You may be able to see this stuff evaporate if you take a few images while the camera runs without the cooler.
Steve, It appears to be internal condensation. I would bake the desiccant plug and of course remove the o-ring first. Make sure to inspect the o-ring. Regards Tim
Tim-Gregg, Thanks for the responses. My first thought, this has been going on for a while, is that it was internal to the camera. My past experience with frost was much different and you could see it dissipate over time by warming up or turning off the cooler. The behavior on this has been very different and similar to when I first received the camera. It comes at the end of my imaging sessions or hours into it. My experience with frost was watching it form as the cooler took the temperature down. Presently the camera is cooled to -15C and running anywhere from 46-60% by time this shows up. My imaging runs have been starting around 9-10 pm using ACP Expert and the observatory usually starts up and hour or two before imaging time. The camera is set to cool to -15C and is started in this startup period with the roof open. At this point the issue seems to be showing up long after the ambient temperature has settled to the lowest it's likely to get that night/morning. I don't see this until I get up the next morning and transfer the images over to my office computer for processing and backup. That's way I though maybe it was dew. If dew was going to form that night/morning it would be under those circumstances. As read through the posts though I remember having this issue when I first got the camera. Seems I had Bill install another heater to eliminate the problem. So maybe the heater isn't working now or a problem with the power supply? I hate to spend the funds to return the camera if it doesn't solve anything. The only other problem I've ever had with this camera is it lost its identity once and we were able to resolve that through the use of CCDOps. It was tricky getting the guider to work as a 237 vs 211 chip but it did work.
