Thought this might be interesting to some; though there's nothing unexpected here, it's sometimes nice to put something visual next to the numbers.
I'd decided to play around with short exposures again, this time with the Sombrero and 36s L. I chose 36 seconds because, based on my attempt at following someone else's math, I believed I could get around 90% of the SNR I was getting from 480s subs, given the same overall integration time, and I thought this might help avoid clipping brighter stars. In fact, the core of M104 is so bright that my normal 480s L subs were blowing the core of that, let alone the stars.
I'd also hoped that by having more, shorter subs and weighting the images by FWHM/eccentricity, smart stacking algorithms might make slight improvements to the overall sharpness when compared to what essentially amounts to a "dumb average" by just exposing longer.
I wanted to do a side by side comparison of the subs to see how much practical difference each 10 subs were making. How much detail was becoming apparent that was previously hidden by the noise?
I never really thought about it before, but as the chart shows, when we're dealing with this amount of short subs, the SNR trend is almost linear.
Signal was calculated as the mean of the cropped area. Noise was calculated using PixInsight's NoiseEstimation script. Both calculated when the image was still linear, of course.
These images are all crops of drizzled (scale 2, drop shrink 0.9) integrations with the exact same histogram adjustment applied. I had to scale down the image for submission here, but the full res is available on
Astrobin.