I noticed that the intensity level of my images was lower than I expected. I normally start taking short exposures and watch the counts until the background comes down as it get dark. But the counts were too low. I was able to reach temperature just fine. I could take images just fine. they were just too dim. Its like the gain was off. So I tried going back to the ASCOM driver instead of the ZWO native driver and the give the same results. I rebooted my computer and re set up with the same results. I looked down the OTA and saw no evidence of frosting and the images showed no evidence of fogging. they looked perfectly normal, just dim. I tried changing gain settings from 76 to 200 and the intensity responded but still lower counts. I moved to my heart nebula target and took 300s Ha subs and compared then to the previous session and again they looked just dim. It was late and I saw no evidence that this was dew or fogging so I just let the data collect.
After work while still daylight, I looked again down the OTA to check and I could clearly see the sensor and the optics looked fine with not fogging or dew. So I set up my flats and LED panel. I compared flats intensities with my standard setup and instead of 31000 ADU I was getting 28500 ADU with the same settings. I am at a loss here to explain this, but it is an issue. I removed the camera and opened it to check the desiccant tablet. They looked fine and so did the sensor. I microwaved my desiccant tablets and re-installed them. I saw no film or any clear moisture on the sensor while it was open. I reinstalled the camera and retook flat with no change. Still about the same lower intensity.
I simply looks like the gain setting is off and I am not getting the gain expected for the setting in the software. I have tried multiple computes, USB3 cables and both the native and ASCOM drivers with no change. I can talk to the camera, get data from the camera with out issue. The images are just like they have a lower gain setting. I verified that both drivers are set at 16bits also. The dark frames are also off from my library for this camera - also like the gain is wrong. I have no problem cooling the camera.
I have an ASI1600MM-COOL on my SCT that I can move over and test also, but I think at this point I would like some outside input on what could be the issue.
Could you upload the fit file of good and bad picutures?
So I can make a compare of them?
please make sure they use the same parameters and same OTA.
Please also try to adust the offset to let the histogram show its left part.
Offset Average Counts (16-bits)
I took a 300s dark frame at -10C with gain 200 and compared to my dark frame master
new dark MasterDark
This looks more like a problem with the gain and not the offset.