Leo Triplet 2022-02-26, how efficiently am I gaining signal per hour of integration?

[pipnina]

I've done a few images this week, including one (which I've considered a bit of a failure) of the california nebula. I am however rather pleased with this leo triplet image, which represents the longest integration of any image I've made to date. Despite that it has caused me issues and poses questions.

First is the odd radial colour banding which occurs when I apply flats, as well as that flats seem to over-correct no matter what exposure I take them at (I tried getting one channel almost touching clipping, then 1/3 stops down until all three channels are averaging around the middle of the histogram, all do the same thing seemingly, maybe the centrally-histogrammed ones over-corrected slightly less). Googling suggests this is either because of my Nikon D3200's RAW frame compression, or perhaps to do with its method of white balance that dynamically adjusts the gain of each channel, or maybe it's the micro lenses, who knows.

The other, is that I feel I am not going very "deep" OR "clean" given the time I am putting into these images. I felt rather good when it comes to my earlier M42 this week but considering this Leo image consists of almost 5 hours or light frames, I thought the galaxies might appear cleaner or I'd be able to see more signs of their fainter "auoras". How does this image compare to some of what you guys have gotten in the same time? I'm wondering if my DSS settings might be non-ideal or if maybe I need to think more seriously about spending on a proper astro-cam.

Either way, it seems the weather is set to change for the worse astro-wise now, and I'm pretty pleased to have gotten the images I have from this week.

Hope you guys got similar luck with the weather.

[scotty38]

Looks pretty good to me but is it possibly black clipped a little and hence why you're missing a bit of the galaxies?

[pipnina]

2 hours ago, scotty38 said:

Looks pretty good to me but is it possibly black clipped a little and hence why you're missing a bit of the galaxies?

Yeah it was hard for me to choose a black point. Technically this isn't clipping because I think all of the pixels have a non-zero brightness. But the background is a bit dark. I couldn't work out a balance between the background looking pitch black when my monitor was on 0 brightness vs it looking washed out and grey when my monitor was at 100 brightness...

[scotty38]

Maybe not an apples with apples comparison but did you see this?

 

[The Lazy Astronomer]

1 hour ago, pipnina said:

Yeah it was hard for me to choose a black point. Technically this isn't clipping because I think all of the pixels have a non-zero brightness. But the background is a bit dark. I couldn't work out a balance between the background looking pitch black when my monitor was on 0 brightness vs it looking washed out and grey when my monitor was at 100 brightness...

I don't know what software you use, but rather than set the black point subjectively (by judging the brightness by eye), you could consider setting it more objectively, by moving the black points such that the pixel values of the background have equal intensity in RGB, and are around 5 - 10% of the maximum pixel value.

[pipnina]

4 hours ago, The Lazy Astronomer said:

I don't know what software you use, but rather than set the black point subjectively (by judging the brightness by eye), you could consider setting it more objectively, by moving the black points such that the pixel values of the background have equal intensity in RGB, and are around 5 - 10% of the maximum pixel value.

That's a good idea. I fiddled with it a bit more and got the average backrgound value somewhere around 10% (so because of noise pixels in the background are going between 6 and 14%)

I also found that RawTherapee supports adjusting saturation by brightness level as a curve, so I have made the background look a lot cleaner too as a result.

I am still not sure how to solve the atmospheric chromatic abberation I see throughout my image however : ( it's almost making triple galaxies in the backrgound in one or two places.

Thanks for the tip : D

[The Lazy Astronomer]

That seems to be a pretty good brightness level there. For further improvement, you possibly have some stacking artifacts as the top and left edges of the frame are noticeably brighter, so maybe consider cropping those. And then maybe there's a slight gradient, as bottom left corner looks darker than top right (excluding areas affected by stacking artifacts, of course).

[scotty38]

Great improvement, nice one!