[glend (Glen)]

I have just conducted a comparison imaging run with the 1600 using SGP .15 and APT. The camera setup was identical for both, the original USB3 cable direct into my laptop. ASCOM driver was .5 as recommended by ZWO currently. Camera setting was Unity, with USB at 45 for both tests. Target was NGC 6188, which I have imaged before with SGP and the 1600 back when everything worked smoothly. I was shooting Ha subs of 300" in length. Focusing and Framign was done in SGP, and the Take One worked fine, and each of the short (10") sub focus and frame shots were clear and target visible.
The mount is an NEQ6Pro, the Scope is a Skywatcher MN190 Mak-Newt f5.3 . The same gear I used for previous successful runs. The mount was guided by a ZWO guidescope and an ASi130 as the guide camera as per the last couple of years of imaging.

The test run consisted of 8 x 300" Ha subs. Started first with SGP, and watched every single sub come up on the display and checked the histogram. The first two were fantastic, with clear definition of the object gas clouds, a good fat histrogram spread across the display, peak about 25-30% from the left side. The 3rd sub through the 7th sub were absolute garbage, the main stars were just visible and the rest of the image was just a patterned noise, all of these subs were identical. The histogram was way over to the left side - no significant signal data. Then suddenly the last sub in the sequence came good again and was the equal to the first two, in content and histogram.
So I had three random good subs out of eight.

I switched over to APT, same setup, 8 x 300" Ha subs, and I watched the subs as they came in. I did a short test sub and it looked fine with a good histrogram, then I started the sequence; the first one was good with the same fat histogram as SGP produced, then the second one was garbage, as was the third and fourth. I terminated the test at that point and went back and checked the output files for both runs. The good subs looked identical whether captured by SGP or APT, the bad subs also looked identical for SGP and APT - the same pattern noise and very low signal shoved way to the left on the histogram.

So my conclusion is that the problems with these ASI1600 images has nothing to do with the capture application, both SGP .15 and APT produced identical good subs and bad subs, but in different quantities and timing in the sequence.
The ASCOM driver .5 was set to the identical setting and USB level for both runs.

Where does this leave us? Well for me, its pointing to the camera and the camera driver/ASCOM driver. There is something very wrong in there. Why did this system (1600 and SGP) work flawlessly for three weeks of imaging and then suddenly stop? Is there a hardware fault that shows up after some hours are put on the camera? I can't say and it's not for me to solve. ZWO has some work to do here. I will cut this post and email it to Sam.

I am stopping any further use of this camera until I get some answers that make sense. I am sick of the frustation.