Juno16 wrote: ↑Wed Nov 29, 2023 1:57 pm
Absolutely the stars are the biggest issue. I definitely could use improvement there.
Are you going to try using his guidelines for exposure time? What time will you try for your location?
My sky is bright, but I really don't want to go below 30 second exposure times. Actually, I haven't gone below 60 seconds.
If we agree that the star saturation is the biggest problem, then we focus on the gains where we have the most headroom.
Your 533 sensor is actually very similar to my 2600 in terms of read noise and dynamic range, it is just 14 bits instead of 16.
So, the e-/ADU gain graph is a factor 4 higher with the 533 because of those 2 bits.
The places where we have the most headroom is at 0 dB and right after 10 dB (100 in ZWO units).
Looking at the last slide for
Bortle 5.8, the ADC value relative to the full well at 0 dB is 3467/52428=0.066, whereas at 10.01 dB it is 587/16580=0.035. That means that there is more headroom at 10.01 dB.
Keep in mind that these numbers are based on a ratio estimate of stars vs.
LP that is based on one of my images. That ratio depends entirely on how many pixels are covered by a star. My rig has a larger focal length, the collimation is flopping around like crazy, the G11 is struggling with the 65 lbs., so I bet your stars are much smaller and that ratio will be higher in your case. So, adjust it based on what you see in the histogram.
Anyway, continuing the line of thought, we stay at either 0 dB or 10.01 dB and increase the sub exposure to the point where the stars start clipping. In our case, the 10.01 dB point looks best to start with.
That's what I can come up with so far, I hope it makes sense because I am making it up as I go.