I was just reading the FR post on Sky Flats, and it reminded me of something I was thinking about the other night; “Auto Exposure”.
I used to live at a darker location and imaged with a DSLR. exposures were always 8 min and always gave good histograms.
Similar with a debayered or monochrome DSLR and narrowband, in that exposure times were consistent over the night and between targets (however I acknowledge that a small gap to the left of the histogram was the only exposure criteria).
Now I have cooled cmos astro cameras, both mono and OSC ZWO ASI1600s. I got the mono camera just before moving from the fairly dark site and was super happy with early Nebulae results at “minimum read noise” gain and 300 second exposure (I was clipping stars however).
Then I started reading the endless threads on short exposures with that camera and started messing with gain, offset, and exposure settings to match various guidelines posted, and, to quote from the above mentioned Sky Flats post, “it’s like trying to pin jelly to a wall”, especially at my new light polluted location.
Yes now I am aware of both a minimum or median ADU target AND the desire not to clip or saturate stars, but the needed exposure seems to be very inconsistent over the night and/or between targets, moon age, etc. Even to the point where I can decide on a setting and then find it is too fast between finishing all the per filter test exposures and running the sequence!
So, the FR, similar to auto focus, could we not have auto exposure? Input criteria would be median ADU and maximum ADU. Figure it out per filter ahead of the run, and adjust periodically (like focus) as the sequence runs.
And, hey, it would be handy for Sky Flats too (median ADU could set at 45000 for example).
Bonus points a way to transfer the auto exposure times to a darks sequence.