Bode's Galaxy in HaRGB - first light 533MC OSC. Comments?

[Padraic M]

I've just finished first light with the ASI533MC Pro. I've spent the weekend in Bortle 2 but with a full moon and a breeze so good conditions but not ideal. Bode was a good test subject as it was at a good remove from the moon.

The 533 is very easy to handle with the SW 150PDS and TS coma corrector - just using the spacers supplied with the camera to give the correct back focus. I could cool to -20c when outside, but couldn't match it the following day to shoot darks, so the image below is shot at -20c and calibrated with -15c darks. I'll shoot at -15c or -10c in future. 

Stacking RGB in APP is a lot more straightforward than mono too - one workflow rather than three! 

On the downside, I'm surprised that there wasn't more colour in the final image. The galaxy is a jaundiced yellow straight out of APP, and the stars are also yellow. APP star colour calibration (csc) washed out the galaxy and still didn't add much colour to the stars. I experimented with galaxy-only and star-only frames using Starnet++; also tried Startools; but in the end settled with a lpc-cbg (no star calibration) output from APP with some ASI1600MM Ha added from an earlier session and finished in Gimp.

Total exposure is 3hrs 20m RGB + 2hrs 45m Ha.

I've continued to struggle with flats for the 150PDS as it leaks light, but I think I have it sorted now - there is light ingress from the secondary end, and also around the focuser drawtube. There were some remaining circular bands of brightness but thanks to @mackiedlm's recent capture, I've realised that they are actually IFN!

Any comments on better star colour or size appreciated.

[Pitch Black Skies]

On 20/03/2022 at 11:25, Padraic M said:

I've just finished first light with the ASI533MC Pro. I've spent the weekend in Bortle 2 but with a full moon and a breeze so good conditions but not ideal. Bode was a good test subject as it was at a good remove from the moon.

The 533 is very easy to handle with the SW 150PDS and TS coma corrector - just using the spacers supplied with the camera to give the correct back focus. I could cool to -20c when outside, but couldn't match it the following day to shoot darks, so the image below is shot at -20c and calibrated with -15c darks. I'll shoot at -15c or -10c in future. 

Stacking RGB in APP is a lot more straightforward than mono too - one workflow rather than three! 

On the downside, I'm surprised that there wasn't more colour in the final image. The galaxy is a jaundiced yellow straight out of APP, and the stars are also yellow. APP star colour calibration (csc) washed out the galaxy and still didn't add much colour to the stars. I experimented with galaxy-only and star-only frames using Starnet++; also tried Startools; but in the end settled with a lpc-cbg (no star calibration) output from APP with some ASI1600MM Ha added from an earlier session and finished in Gimp.

Total exposure is 3hrs 20m RGB + 2hrs 45m Ha.

I've continued to struggle with flats for the 150PDS as it leaks light, but I think I have it sorted now - there is light ingress from the secondary end, and also around the focuser drawtube. There were some remaining circular bands of brightness but thanks to @mackiedlm's recent capture, I've realised that they are actually IFN!

Any comments on better star colour or size appreciated.

Really nice 👍

Mine seem to end up looking unrealistic.

Any ideas?

[Felias]

It looks greenish on my screen, not yellow. I have tried using Siril's photometric calibration, and it seems to get better, though it's rather reddish. But I only had your already calibrated jpeg to start with, so I didn't expect it to work perfectly. Maybe you could try with your stacked tiff/fits file, and remove the green noise if it doesn't completely go after the calibration.

 

[Padraic M]

3 hours ago, Pitch Black Skies said:

Really nice 👍

Mine seem to end up looking unrealistic.

Any ideas?

I don't think that's unrealistic at all. Lots of great detail in both galaxies, and you've captured the starburst red in M82. Obviously the crop shows some 'artistic license' 😀, and in my opinion the background is too black - I suspect you may have clipped some of the darker detail. I can't really see the star colour or star shape from the final image.

[Padraic M]

2 hours ago, Felias said:

It looks greenish on my screen, not yellow. I have tried using Siril's photometric calibration, and it seems to get better, though it's rather reddish. But I only had your already calibrated jpeg to start with, so I didn't expect it to work perfectly. Maybe you could try with your stacked tiff/fits file, and remove the green noise if it doesn't completely go after the calibration.

 

Interesting - thanks for that pointer. I've just had a beginner's play with the latest Siril and it looks very good. Here's a quick version using 100 1-minute lights with corresponding darks, flats and dark-flats. RGB OSC only. I have to figure out how to add Ha. I also need to understand how to manage noise, as it's quite obvious here. Other than that it's a lot better than my first attempt.

[Felias]

11 minutes ago, Padraic M said:

Interesting - thanks for that pointer. I've just had a beginner's play with the latest Siril and it looks very good. Here's a quick version using 100 1-minute lights with corresponding darks, flats and dark-flats. RGB OSC only. I have to figure out how to add Ha. I also need to understand how to manage noise, as it's quite obvious here. Other than that it's a lot better than my first attempt.

Definitely better! 👍 Perhaps still a bit green? Removing the green noise in Siril takes just the click of a button. I was having trouble myself with getting the right colours until I started using photometric calibration. As for the noise, I have lately been doing successive asinh stretches, followed by a levels adjustment in PS. This has kept the noise from messing the background too much, and has made it easier to correct with a filter when I have finished stretching.

[Padraic M]

Great. I'm definitely going to play more with Siril.

[Pitch Black Skies]

12 hours ago, Padraic M said:

Obviously the crop shows some 'artistic license' 😀

Don't know what that means. Are you referring to the name of the file being very long?

"in my opinion the background is too black - I suspect you may have clipped some of the darker detail."

When I make it brighter, the galaxies tend to look animated or CGI.

[Padraic M]

@Pitch Black Skies re the crop comment - just that in trying to keep both M81 and M82 in frame, you've lost the left-most edge of M81.  It's always a temptation with this pair if your field of view isn't wide enough to fully fit both. My approach at the moment is to do both separately, and see about a mosaic at some stage in the future when I have enough data on both.

On the dark background - I see from other posts that you're using Startools. I know that others can get great results from Startools but in spite of spending many hours with many images in there I've never managed to get it right. If anyone can guide you through that process, Alacant can. In your other posts I can see the typical 'blotchy' dark background that I get with Startools.

In the meantime, you could try the basic levels and curves approach in Photoshop or Gimp - it won't give super results, but gives a good understanding of what is happening with dynamic range adjustment. I loaded your jpeg into Gimp below - adjusted the mid point down slightly to stretch the histogram just a tiny bit, and then pulled the black point up slightly to retain the overall contrast level. This reveals more detail in the background - possibly IFN.

My workflow is very simple - I stack in AstroPixelProcessor (which is a step up from DSS) and do some basic image processing in APP such as light pollution removal, star colour calibration and a light stretch. Then in Gimp to adjust the levels as above, boost the colour saturation and finalise the image including bit-depth, size and file type.