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M42 RCC

Request for feedback
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Arun H avatar
Arun H avatar
Hello -

I am looking for constructive criticism on this M42 image. I am mainly looking for processing tips that maximize the dynamic range presented including star color. I know there are some limitations that are likely impossible for me to overcome given my conditions - bad seeing, lack of integration time for example. But mainly I am looking for suggestions on how to make the best of the data already captured. This is a pretty hard object to process well, at least for me. Thank you for your time.

https://astrob.in/q3caa2/
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andrea tasselli avatar
andrea tasselli avatar
You need to claw back some dynamic range to accommodate the stars without blowing out the cores. I suggest to keep your shadow point considerably below what you have now. Not sure what I used but I think I was working with AutoHistogram to start with as initial stretch.
Arun H avatar
Arun H avatar
Thank you Andrea.

This was done using GHS. Yes, indeed, the star cores are the biggest issue I see with this image and I am interested in ways to preserve them. 

The typical approach is to use StarX etc., and work on the nebula and stars separately. Unfortunately, this does not not work on this object because the stars are not cleanly removed. I have seem images which do a better job at this than I was able to and so am very interesting in learning what worked.
andrea tasselli avatar
andrea tasselli avatar
I'm pretty sure I started with that so maybe you could try that too. I was interested in preserving the Trapezium so this is what I got:

Working with 60s integrations was a hurdle as far as star core colour was concerned and you can forget about it in the nebula's core.
Chris White- Overcast Observatory avatar
Chris White- Overcast Observatory avatar

Ive got data on this target to process soon and will average the same struggle as you. I think that for me, its ok to have a very bright trap. Compress the DR just enough to make out details but without getting an HDR cooked look.

Dont forget, that the trap is really bright in real life! Your inage looks great.

John Hayes avatar
John Hayes avatar

Arun H · Dec 24, 2025, 03:40 PM

https://astrob.in/q3caa2/

Arun,

Although M42 is commonly imaged, it is a very difficult target—as you know! My general suggestions are:

1) The black point is a bit too high.

2) The stretch isn’t quite right and that’s producing a very flat appearance. It’s been a while since I processed my image of the same target but as I recall, I stretched it multiple times to get a good balance between the bright, mid-tone and dark regions. You might check it out to get a better idea of what I’m talking about.

3) Taking enough exposures to create a HDR image is really helpful—even if you just try to save the Trapezium. That was the only way that I was able to show the trapezium in my image.

4) Your colors are a bit muted. This is a very colorful object so I would add some saturation and vibrance to “punch up” it up a bit more.

5) The stars in this region are hot and blue but somehow the star color is being lost—or at least the color isn’t prominent enough. Try to figure out how to recover that color. If the stars are saturated in the original data, that won’t be possible—so be careful to avoid overexposed stars when you take the data in the first place.

It looks to me like you’ve got some good data so keep messing around with the processing and I think that you can arrive at a spectacular result.

Good luck!

John

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Arun H avatar
Arun H avatar
@Chris White- Overcast Observatory - Thanks for your comments and I look forward to your image. I have every expectation, given your other work, that it will be amazing and something I can learn from.

@John Hayes Thank you very much for the feedback. I am very familiar with your M42 image. I have not bookmarked it - but that is because I know exactly where to find it and who took it. I have referred to it many times, and indeed it is the reason why I feel my processing can be improved. I cannot match your seeing and resolution, but I feel like the data I have should come closer to your color and presentation of dynamic range. If what you used for your image was standard processing tools (like GHS, HDR transform, curves, saturation etc.) then I have direction that I just need to try harder. The stars are definitely not saturated in the original data, so I should be able, with effort, to recover color much better than I have. Thanks again.
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