Help with IC 1396

[nucdoc]

 

I would not mind some input and suggestions.

 

This is a preliminary version, I have collected 3.5 hour of 3nm Ha data, and finally on the weekend was able to collect 40 min each of LRGB, I used my usual processing technique in PI with some final tuning in PS. Atik 383l+, Tak 106N, Chroma 3nm Ha filter, and Astronomik RGB filters, Astronomik CLS CCD filter for L

Flats, Darks, Bias all applied, DBE, color calibration, background neutralization etc.

 

I am wondering why the image is so dark, is this typical for this part of the sky, or is this a result of the imbalance between NB and LRGB data, will it get better with more LRGB data? or have I messed up the processing

Thanks

 

Mark

 

[sharkmelley]

That area of sky has a lot of H-alpha - just do a Google Image search for IC1396 and you'll see lots of images full of redness.  It's difficult to say what has gone wrong in your image.  One possibility is that that the H-alpha has been mistaken for a background gradient and subtracted from the image - this is far too easily done when using DBE.  To be fair, distinguishing background gradients from true data is frequently one of the biggest challenges in astro-image processing.  On the other hand it could be that the balance between your H-alpha data and the LRGB data is not quite right.

Mark

[nucdoc]

Thanks Mark for you comments.  I did the DBE on the LRGB image, and the Ha image separately before I combined them, but is is possible that the DBE on the LRGB over subtracted the red nebulosity.  Also, the script that I use in PI for adding Ha to LRGB has been removed from the most recent upgrade, they have substituted a NB combination script that I have never used before so there is certianly a possibility I did not use it correctly,  I think I will go back to using PS to add the Ha in the red channel and see if I have better luck

 

Mark

[andrew s]

Remember there are no absolutes in astro images. Each is processed to give a pleasing image and considerable "regression to the norm" takes place. I.e. imagers process their images until they match what their peers have done.

I find your image engaging as it is with the dark lanes showing well.

Regards Andrew

[ollypenrice]

7 hours ago, andrew s said:

Remember there are no absolutes in astro images. Each is processed to give a pleasing image and considerable "regression to the norm" takes place. I.e. imagers process their images until they match what their peers have done.

I find your image engaging as it is with the dark lanes showing well.

Regards Andrew

I agree with this. In my own 'Elephant Trunk' I thought, 'To hell with all that Ha signal, I want it only to enhance the LRGB where it is very strong.' A great pink sea of flat Ha has nothing to be said for it.

My question is this: what does PI do with Ha when blending it? When I add Ha to LRGB in Photoshop I know (and can control) the extent and the manner in which it is applied. I really wouldn't want to use some opaque script which just did what it did without letting me control it, but maybe PI does offer this control?

Olly

[RichLD]

I really like it!

[nucdoc]

Thanks, appreciate the comments and suggestions.  The NBRGB combination script does offer some control, but I am not sure I am fully confident in my understanding of it.  The script that was in the previous version (now removed, or moved to a place I cannot find) had a function similar to the opacity function of PS and I found it easier to use.  I did try to use PS but my experience is limited at combining LRGB with Ha in PS, and in this case it seemed to come out more diffusely red.  I have appended a new version using PI,  I used to star Halo reduction function in PI and played with curves and the histogram a bit more to try and clean up the stars and increase contrast, I think I like this version a bit better. It is surely a dark and moody patch of sky !

 

Mark

 

[alan4908]

On 8/16/2017 at 01:29, nucdoc said:

Thanks, appreciate the comments and suggestions.  The NBRGB combination script does offer some control, but I am not sure I am fully confident in my understanding of it.  The script that was in the previous version (now removed, or moved to a place I cannot find) had a function similar to the opacity function of PS and I found it easier to use.  I did try to use PS but my experience is limited at combining LRGB with Ha in PS, and in this case it seemed to come out more diffusely red.  I have appended a new version using PI,  I used to star Halo reduction function in PI and played with curves and the histogram a bit more to try and clean up the stars and increase contrast, I think I like this version a bit better. It is surely a dark and moody patch of sky !

 

Mark

Hi Mark

Having just finished my own effort on IC1396, I have to concur that it is a difficult object to process. My own LRGB image was too dim, so I decided to blend it with a mixture of Ha, OIII and SII basically in an attempt to brighten it up and enhance detail, however, I was also keen to maintain the approximate RGB colours. Having experimented with both PS and Pixinsight, I decided to first experiment with how to map the NB information to RGB. I eventually settled on RED to (0.5*SII)+(0.5*HA), GREEN to 0.2*HA+0.8*OIII and BLUE to OIII. I then blended this with my LRGB effort using the Pixinsight script NBRGBCombination - you can find it in the SCRIPT->Utilities->NBRGBCombination. My knowledge of using this is limited to simply using Warren Keller's book "Inside Pixinsight" for guidence, so after a little experimentation with the slider controls, I ended up with something that I was happy with. 

Alan