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LBN437 Ha-OSC on a Samyang Requests for constructive critique · Christopher · ... · 12 · 332 · 5

Christopher 0.00
Christopher
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Hi folks, 
the following image has taken a bit of a toll on my mental health recently. I kinda like it (on a bigger screen), but I am not entirely happy with the end result, especially with how overemphasized the stars look in contrast to the nebulosity. That however has been something I somehow seem incapable of solving.
https://astrob.in/z3m355/0/
the workflow in a nutshell: 
-13hrs osc (2600mc+samyang135) calibrated and stacked using wbpp, the same done with 12hrs ha (2600mm)
-gradient correction using Graxpert
- both images registered and cropped to align
- R-channel extracted and blended with the ha-signal and then combined back into an (ha)osc
- BXT+NoiseXT and several rounds of ghs iterations and a round of star reduction algorithms 
I would greatly appreciate any pointers as to how to improve the overall result. 
Thanks in advance and cheers! 
Chris
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andreatax 9.89
andrea tasselli
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I find the image quite pleasing but I get your meaning about the stars in relation to the overall image. It should be possible to reduce the stars impact but I wouldn't be using CHS at all, just ASINH in combination with HT and possibly CT to tone done the brightest ones. But I do like the way you worked out the stars.,
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astroswell 1.51
Maxim
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Have you tried stretching stars separately? Basically you remove stars when the image is linear, process it, stretch stars(I recommend StarStretch script from seti astro) and then combine the two. This way you have even more control on stars' appearance than just reduction. But you can apply reduction anyway after.
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Carande 2.61
Richard Carande
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I agree with Maxim – processing stars and nebulosity independently is important.
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Alexn 12.25
Alex Nicholas
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I would second Maxim's comment.

I would be removing stars from the Ha, and the OSC data (throw away the Ha stars and just use the OSC stars)
Blend your Ha in to the R channel, then put the OSC starless image back together and stretch it to your desired appearance,
stretch the stars separately, keeping them toned.

Screen those stars back into your starless nebulosity. If you don't like the result, you can always stretch the stars image more, or undo some of the stretching, then go again on re-screening them into the starless image. 

It can be a delicate balance getting the stretch right between stars/starless image, and it will be an iterative process until you get used to doing it..

If it helps - I think your image looks lovely as it is - but I can see why you might want to tone down some of those stars a little.
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Curtis2010 0.00
Curtis2010
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A common technique, and one which I use also, is to create a starless version of the image so that you can work the nebulosity without affecting the stars. I use StarXterminator to create the starless image. Then process a copy of the image containing the original star field separately.  Then blend the two images. 

A step I add to this process, especially for dense star fields,  is to mask out some of the stars on a copy of the image that still contains stars. I then blend the reduced star field image with the starless image to create the final image. 

I use APP + PS so I cant give you specifics  on the process under PI, but here it is in general.

- stack subs to create a complete original image
-  create 2 copies of original image (one which will have stars removed, one which will not)
- remove stars from one copy of image. 
- adjust starless image as desired
- mask stars in the other original image copy (I use a luminosity mask tool, TK Luminosity Mask, in PS to do this). Select stars based on luminosity until you have the density of star field that you want. 
- blend the starred and starless images together. 

Example images from a wide FOV of IC 1396 (Elephant Trunk): 

Original:


IC_1396-RGB-session_1 original small.jpg

Blended:

IC_1396-RGB-session_1-St PS small.jpg
Edited ...
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Curtis2010 0.00
Curtis2010
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Example of method I posted above using your image:

Example_JwtGTIUT0jA_16536x0_LJKVaCNk.jpg
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Die_Launische_Diva 11.54
Die Launische Diva
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At a first glance I don't find any issues with your image. Some may say that the medium-sized to small-sized stars are too sharp but that doesn't bother me at all. Your field of view is not that far from the galactic equator and for that it is expected to be packed with stars. I find that going too far with star reduction (like the above example image) is towards the wrong direction. I definitely prefer your approach on star reduction more than the image presented above, for which even astrometry.net platesolver may struggle finding stars.
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Christopher 0.00
Christopher
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Hi all! 
Thanks a lot for your advice and ideas! I will try to put them to practice, but will aim to keep it balanced as @Die Launische Diva  suggested considering its coordinates within the galactic plane. 
I appreciate you guys! 
best regards Chris
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Curtis2010 0.00
Curtis2010
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It comes down to personal preference. I like significantly reduced star fields because it reveals much more nebulosity detail without being as stark/unnatural as a completely starless image. 

Using a star mask you can of course adjust it to you presonal preference. 

Another version of Christopher's image below with a much less reduced star field. I quite like this verison. 



Example 2_JwtGTIUT0jA_16536x0_LJKVaCNk.jpg
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Christopher 0.00
Christopher
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@Curtis2010  that Version sure brings out the nebulosity a lot more! Thanks for demonstrating! This is sort of the type of star reduction I was hoping for. Will need to sift through the raw frames again to eliminate the ones causing the star halos. Once done, I will reprocess.
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Tackettbr 6.24
Brandon Tackett
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I agree with the above. I copy a separate star image in the linear form. I stretch the stars in GHS with realtime preview to where i like them. I then generate the stars only from the GHS stretched and blend them with the non linear starless image that i have adjusted. I recently shot the shame field with my 294mm. The main imaged is cropped but the the mouse over is the full image.



The Red Dress Nebula SH2-126
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Curtis2010 0.00
Curtis2010
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Christopher:
@Curtis2010  that Version sure brings out the nebulosity a lot more! Thanks for demonstrating! This is sort of the type of star reduction I was hoping for. Will need to sift through the raw frames again to eliminate the ones causing the star halos. Once done, I will reprocess.

Yes, those halos could use some work.  I agree that its probably just a few subs, maybe some thin cloud passed over. 

Maybe push the star color up some too. Masking this way does tend to dampen the star colors.
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