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I also noticed the inside of the objective lens was a bit foggy so I brought the whole system in, seperated the scope from the filter wheel and from the camera and dried them all out in the boiler cupboard (drastric measures !).
I have now reassembled and returned them to the observatory and ordered a usb dew heater strap for the objective, coming later today. If needed I will order another one to sit as close as I can get it to the filter wheel. Then when we get a night without cloud in what’s left of 2020 I will try it all again.
I have seen an option where you can take off the imaging camera and add a “dew cap” to the end of the scope and inside sits a dessicant pouch. This should keep the filters and inside of the OTA dry. The problem with this is you have to take off the camera each time and it spoils any setup (orientation and focus) I have achieved. Also it only works until you start imaging and as I have experienced, dew can form in the first hour of observing.
Although dewing and the desiccant sounded the potential problem, it turned out to be something else.
As I dismantled the camera off my telescope to prepare to dry the desiccant, I noticed the fiield flattener I was using on my refractor looked a little dirty. However, when I tried to clean it it seems the dirt is caught between layers of the flattener I cannot reach. See image.
Oddly the appearance of this dirt varies and a stable room temperature looks like it completely disappears. Must be at its worst when its super cooled ?
So I redid my flats with the field flattener removed and the images are all fine and do not change over time. So no need to dry the desiccant.
However I have had to send the field flattener back to the company I bought it from to be professional cleaned.
Still very grateful to you for your advice though.
Could not wait to get my darks and flats ready so went out and took my first image. Just 15×40 second subs using an Ha filter. Really pleased with result. Cant wait to do more with this new camera.
The gain goes upto 30 maximum. But at that setting the well depth is only 512 so not worth going that far.
Thanks George. I actually have a good and stable imaging system with a pier mounted EQ6-R with autoguiding inside an observatory and I have built, so long exposures isnt a problem. With my ATIK 314L+ CCD camera I was doing 5 minute exposures without issue. Whats the problem doing much longer exposures than 40 seconds with the CMOS camera ?
