M42 (if you haven't seen enough of it already :D) - Forums

Topic starter

Dec 28, 2019 · Edited: Dec 29, 2019

Good day everyone,

I am seeking some critique over my images as to where I can do better. Here is my latest version of the Orion's nebula using my recently purchased SW Esprit 100 ED: https://www.astrobin.com/zsckfk/P/?nc=user

Processing this image took very long, probably 5-7 hours. I used approximately 1.5 hours of color data per channel and combined it with 2.5 hours worth of Ha data. I did not use the Ha data as a "pure" luminance layer on top of the image but rather as a selective masked luminance layer to enhance the dust and dim nebulosity at various stages during processing.

Microlensing and internal reflection of the filters are some of the challenges that had to be overcome with this image. I tried to do so to such an extent without harming the data in the regions.

Thanks for taking the time to look at my images.

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Shawn Killian

Dec 28, 2019

Hi Janco, very beautiful m42! Looks great to me, I think you will be hard pressed to get it much better! Clear skies S.K.

Samuli Vuorinen

Dec 28, 2019

Wow, I really like it! It's maybe a bit too purple for my taste, but the detail and processing is otherwise really great!

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Janco

Topic starter

Dec 28, 2019

Thanks for the feedback guys.

Samuli Vuorinen:
Wow, I really like it! It's maybe a bit too purple for my taste, but the detail and processing is otherwise really great!

Samuli, now that you mentioned it I completely agree. I've reduced some of the overwhelming purple color and reduced the saturation ever so slightly. Looks better to my eye now. Thanks for the suggestion

Gabriel R. Santos (grsotnas)

Dec 28, 2019

Janco, that's a beautiful image of M42. Here are some things I noticed when vieweing the image.

- Your data looks pretty clean, the integration is deep enough, and the HDR composition worked wonderfully - something I've never managed to do it right myself [perhaps you could share some tips on how you blended the core exposures? =D]

- Your handling of the microlensing effects was very good - those 1600 sensors are (in)famous for it, but your image barely shows anything [it also hasn't the brightest stars out there, but anyway, I liked the stars]

- Your Final [M] Revision looks too purple/magenta to me as well. It was greatly improved in Revision N. However, I believe your image could use a bit more blues. My M42's have "bluer" outer "arms", and the area around the Running Man features more blue (IMO, and to my taste). Perhaps this colour was somewhat subdued in processing - you might want to restretch the data. I see you do not use PixInsight, but its PhotometricColourCalibration tool is very useful in getting good colour balance, from the start [most of the times]. The blue may also had been lost in Gradient/Background subtraction. Which tool did you use to make this step? Finally, adding Ha to the data will probably make the blues stand out less, since there is also a "background" faint Ha signal over the whole area. It may also be something of taste, but that was my experience (with OSC DSLR imaging. So, no narrowband Ha).

- Your N revision, despite helping the Magenta cast, created some strange greenish background in the deep shadows [especially in the upper left]. A pass of HLVG (perhaps with a mask) could be helpful.

- Personally I prefer the "horizontal" orientation, East up. However, that's a completely minor point.

- I really liked the sharp details in the core of M42. Nicely done!

Overall, that's a very nice image! And I see you are at a similar Latitude than myself, however on the other side of the Atlantic =D.

Best regards

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Janco

Topic starter

Dec 29, 2019 · Edited: Dec 29, 2019

Thank you very much for taking the time to give your comments Gabriel.

- Your data looks pretty clean, the integration is deep enough, and the HDR composition worked wonderfully - something I've never managed to do it right myself [perhaps you could share some tips on how you blended the core exposures? =D]

Thanks Gabriel! I found what works well for me is to blend the core with the longer exposures stack after I have done some very mild stretching on both images. I simply paste the core as a new layer over the image with a selective mask allowing only the brightest part of the core to be shown. I then go on a iterative process where I do a Gaussian blur (maybe 10 pixels or so) on the mask, stretching the mask and core layer, and adjusting the core colour saturation. I repeat this process until I get an image where the two images are no longer distinguishable from each other and the "flow" from the one to the other appear to be as natural as possible. I prefer to keep my core on the bright side because it is the brightest part of the object and find it easier to look like it is part of the image and not simply another layer you stuck on top of it.

- Your Final [M] Revision looks too purple/magenta to me as well. It was greatly improved in Revision N. However, I believe your image could use a bit more blues. My M42's have "bluer" outer "arms", and the area around the Running Man features more blue (IMO, and to my taste). Perhaps this colour was somewhat subdued in processing - you might want to restretch the data. I see you do not use PixInsight, but its PhotometricColourCalibration tool is very useful in getting good colour balance, from the start [most of the times]. The blue may also had been lost in Gradient/Background subtraction. Which tool did you use to make this step? Finally, adding Ha to the data will probably make the blues stand out less, since there is also a "background" faint Ha signal over the whole area. It may also be something of taste, but that was my experience (with OSC DSLR imaging. So, no narrowband Ha).

I believe when I added the Ha layer as a luminance layer it might have caused some of the blues to lose some of its saturation. I've attempted to restretch the data ever so slightly to see if I can regain some of the blues in the outer arms and the Running Man. Don't know if it was enough but it seems to be a slight improvement. When processing this image initially I did not apply any gradient subtraction. I use Annie's Astro Actions gradient reduction tool to usually deal with it but in conjunction with a mask of some sort as I found it can sometimes harm colour where you don't want it to. In the latest revision of this image I did use it and it seemed to take care of the green you were noticing.

- Personally I prefer the "horizontal" orientation, East up. However, that's a completely minor point.

Agreed. Fixed! Don't know why I was trying to be funny there.

Once again, thanks for your inputs

Regards

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