M57 Nebula Center Process Issues

[niteman1946]

High Group,

Here is my version of M57 done in Ha, O3 and S2.  I was pleased with obtaining some of both outer shells of this nebula.


While I appreciate there are lots of criticisms that can be launched against the overall product, I'm mostly interested in the center of the nebula.  It certainly does not look like other images, and most likely is the result of over-processing.

The technical data is in the above Astrobin site, about 2/3rds down in the Description section.

If anyone is interested, I've included (dropbox) the following three files for the Ha which was used for luminance.

https://www.dropbox.com/sh/s3cmstxysbg97gg/taUVRcMOdq
1.  file ending in "....DC.fit"
Just after integration and about 50% cropped.

2.  file ending in "....TGVstr200.fit"
Same file after DBE, denoise, deconvolution, histogram, denoise.

3.  file ending in "....smi HDRMT3.fit"
Same file as 2 with HDR Multiscale Transform (layers at 3).

Appreciate any and all comments, and apologize if I've posted in the wrong location.

Thanks,

Mark

[niteman1946]

Any suggestions on how to improve the center?

Mark

[pfile]

i think that 'rippled' look in the core comes from the HDR transform at layer 3. you might try doing it thru a mask to lessen the effect, or use a higher number of layers...

have not had time to look at your data but i saw a similar effect in my own tries...

rob

[jerryyyyy]

I agree with Pfile.  I worked on this object for a while inspired by the Hubble images and wanted to see what I could get with my poor C8. 

One thing I learned is that the exterior rings are mostly H-alpha with O-III.  Your weighting of the narrowbands is heavy on the S-II, which may be another reason why the core is so harsh. .. I think that is where the S-II shows up.   

It would be nice to have a page where all these combinations were discussed.  I have another nebula with another 20h of data and it is hard to figure how to weight what. 

[niteman1946]

i think that 'rippled' look in the core comes from the HDR transform at layer 3. you might try doing it thru a mask to lessen the effect, or use a higher number of layers...

have not had time to look at your data but i saw a similar effect in my own tries...

Thanks Rob. With the layer setting of 5 or lower, the center looks artificial.  Anything above that doesn't bring much to the party.  Currently, I'm masking the stars only -- not sure how I would mask the nebula and still affect it.

It is interesting that you have seen something similar.  I figured this was strictly an artifact of the software.

My gut tells me that HDR Composition (combining short and long exposures) should produce more "realistic" detail, but my one stab at that was not pretty.  Nevertheless, I'll keep trying.
Mark

[niteman1946]

One thing I learned is that the exterior rings are mostly H-alpha with O-III.  Your weighting of the narrowbands is heavy on the S-II, which may be another reason why the core is so harsh. .. I think that is where the S-II shows up.   

It would be nice to have a page where all these combinations were discussed.  I have another nebula with another 20h of data and it is hard to figure how to weight what.

Thanks Jerry.  Good point about the S-II, although the mono image that is used for luminance (ergo all the detail) is the Ha only.  I'm using the contribution of O-III and S-II (along with Ha) for color only.

I'm considering putting some more time into HDR Composition to see if that can pull out more realistic features.

Look forward to seeing your 20hr work.

Mark

[pfile]

i think that 'rippled' look in the core comes from the HDR transform at layer 3. you might try doing it thru a mask to lessen the effect, or use a higher number of layers...

have not had time to look at your data but i saw a similar effect in my own tries...

Thanks Rob. With the layer setting of 5 or lower, the center looks artificial.  Anything above that doesn't bring much to the party.  Currently, I'm masking the stars only -- not sure how I would mask the nebula and still affect it.

It is interesting that you have seen something similar.  I figured this was strictly an artifact of the software.

My gut tells me that HDR Composition (combining short and long exposures) should produce more "realistic" detail, but my one stab at that was not pretty.  Nevertheless, I'll keep trying.
Mark

well, you can extract L* from your image and then use the histogram transformation and/or curves to get the mask strength to your liking. you may have to use pixelmath to combine the star mask you are using and the L mask if you don't like what happened to the stars in the L mask. then you can apply HDRMultiscaleTransformation thru the mask to get a muted effect.

or i suppose if you just want to attenuate the process globally, you can make a mask with pixelmath with the expression "0.5" (or whatever strength you want) and then tick "create new image" and "Greyscale" in the bottom pane.

rob

[niteman1946]

well, you can extract L* from your image and then use the histogram transformation and/or curves to get the mask strength to your liking. you may have to use pixelmath to combine the star mask you are using and the L mask if you don't like what happened to the stars in the L mask. then you can apply HDRMultiscaleTransformation thru the mask to get a muted effect.

or i suppose if you just want to attenuate the process globally, you can make a mask with pixelmath with the expression "0.5" (or whatever strength you want) and then tick "create new image" and "Greyscale" in the bottom pane.

rob

Thanks Rob.

Yes, I see what you mean.  Yet another tool for my kit.  Good old PixelMath.

I'll play with this a bit and see if a more normal center can be achieved.

Mark