Strange artifacts in images

miwitte

Brand new V3 1600MM-C only used it a couple times it worked perfect for 2 nights and captured a couple hours of M81 with no dark spots. I went to go add more integration frames and had odd circular dark spots on upper half of image. Image train has been inspected and is nice and clean so I assume its camera and moisture as I have seen a few others here with almost identical black round spots on their images. It appears to not be there at room temp but as it gets colder it gets worse. I have put the supplied dessicant tube with 2 tabs in yesterday ill give it the 24 hours. Whats concerning is that after only a few sessions outside I am having issues with what appears to be moisture inside the chamber as there are already 4 dessicant tabs in there correct? Any other things I should be looking at? Should I inspect camera window with camera powered, cooled and off the scope? Looking down the optical tube I can see right to the sensor and I don't see frost on the protection glass .

miwitte

did some testing but to show what I had this was first light last weekend with my very expensive camera and filter wheel. Gain 0 Offset 10. Notice nice and clean no little round dots. I ran for a couple hours using LRGB and got good data

miwitte

Next time out a couple days later the camera showed this. I thought it was frost from reading things here.

miwitte

I put the dessicant tube on with two tabs yesterday and have been running tests tonight. Looking at flats with gain 0 offset 10 I get the same pattern. I have rotated camera unscrewing it from filter wheel in various directions and the pattern of dots stays on top of the frame so it is not the optical train. I took camera off inspected it for fingerprints or anything on wndow it is spotless. I also brought it down to -15 de-attached to the filterwheel inspected under magnifying glass and no frost or anything on window or sensor. Not sure where to go from here I got 2 hours of imaging on a brand new camera and now the pictures shown aren't of any use.

Here is a flat taken tonight -15C gain 0 offset 10. You can see the small circles on top pretty much matched what I saw the second night out. Like I said its on the top no matter if I rotate the camera so its definetly the camera.

miwitte

if I bring the gain to 300 offset 50 ADU 20K for flats the noise appears to go away. This makes me think its not frost. This is also using the ZWO power supply for the cooler.

Sam not sure what to try next. Im traveling the next few days would like to figure out what to do when I get back I was really excited about the quality of images I got on the first run but pretty disappointed in whats going on now.

Sam@ZWO

it looks very strange and we didnot hear such issue before

can you try cool it slowly

like cool to 0 degree at first and wait 5 mins cool to -15 degree

miwitte

I wont be home for a few days, but I did try different temps and to cool slow like you said same result. First light pictures were perfect as you can see, I set up gear, powered up and connected via SGPro and was doing LRGB in no time and gathered several hours of good data the first night. Next time out a couple days later first image showed the black round spots on top shown. I have gone through optical train, and since the spots shows up in exact same area even when camera is rotated and filterwheel stays the same leads me to point to something in camera. Also spots are much worse at 0 gain vs 300 gain so I don't think its frost and I don't see any in the window anyway.

Whats my next step here? after 2 nights I shouldn't have a camera with spots like this. Ill try and image again when I get home and cool slow, but first light I did not do that and it was perfect.