Recently, I was experiencing some issues calibrating my HA data (180s/gain 75) as they were all coming out mostly black. After some thought, (and experimentation), I realized the mean value of my darks was higher than the mean value of my HA data. I certainly couldn't use dark optimization effectively with my CMOS (QHY163M) so that was not an option. I solved this issue by manually calibrating the data using a pedestal value of 800DN on my HA calibration.
I then began wondering though, since there was clearly amp glow present in my data and my darks, would that cause my darks to be lighter than my HA. I did a quick test and shot a 3 min. dark using my LUM filter as I usually do and got a mean value of 595 which was higher than the mean of 576 for my HA. I then shot a 3 min. dark through my HA filter and indeed saw a drop to a mean value of 556. I always assumed that the filter shouldn't make any difference to my dark frames. Now, it looks like the amp glow is contributing enough light(?) to make a difference. I am certainly no expert here but is there any validity to this option or should I just keep using the pedestal value? It seems one benefit might be if someone had this issue and wanted to use WBPP and not worry about using the pedestal. It also occurred to me that I could/should have used a higher gain for the NB data.
Either way, this was a great learning experience!
Edited by jonkjon, 22 November 2020 - 11:43 AM.