Author Topic: Adding Ha to nebula image  (Read 19008 times)

Offline dayers

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Adding Ha to nebula image
« on: 2011 September 07 17:25:56 »
I have had good success following Harry's good video tutorial about adding Ha to a galaxy image. Has anyone tried the same general procedure with an image that is mostly nebulosity, like M8? I can't find a set of PixelMath parameters that doesn't result in black "stars" burnng holes in the nebulosity. Trial and error is giving me no joy.

Maybe trying to add Ha to an image that is mostly Ha to start with doesn't make sense.

Dave
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Offline Ioannis Ioannou

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Re: Adding Ha to nebula image
« Reply #1 on: 2011 September 08 00:11:11 »
I'm using something similar, found here in the forum, again mentioned as Vicent's method:

C = r - ha
Ha_clean = ha - (bandw_Ha/bandw_R)*C
HaR = R*r_mult + Ha_clean * ha_mult

The trick is to produce a good C image without too many holes. A few are ok, the final result will take care of them. I have changed it a bit to match different time in subs and different bin, making some assumptions (that I'm not sure if they are correct, at least worked in one case) :

C =  r - (tR / tHa) * ha 

where
tR = time R * bin
tHa = time Ha * bin

But still, in some cases I had to click on "rescale result" in order to get reasonable results. The last time I used it, I first "linear fit" R with Ha and then I produced a very good C  with just C = r - ha .
 
You can see some results here, here, and (a very bad one) here. Zoom in Elephant's trunk and notice that the blue (from reflection) on the nebulosity has indeed been preserved, although Ha in this area is very strong.

What I have found is that you still need GOOD RGB frames, otherwise the final result is not very good.

Since I'm novice on this field, this is just my 2 cents.
« Last Edit: 2011 September 08 00:16:12 by Ioannis Ioannou »
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Offline dayers

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Re: Adding Ha to nebula image
« Reply #2 on: 2011 September 08 09:03:43 »
Hi John,

Thanks for your comments. It sounds like PixelMath is our friend in cases of this kind. I need to find the thread about LinearFit again to see how it might be applied. So much to learn and so little time! I've been using Jim Misti's M8 raw data to practice on.

Dave
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Offline sleshin

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Re: Adding Ha to nebula image
« Reply #3 on: 2011 September 08 15:22:46 »
Dave,

I did add Ha to the Medusa Nebula, an image I posted in the gallery a couple of months ago. Here's the link:

http://pixinsight.com/forum/index.php?topic=3223.0

Ha was combined with the Red master and the new HaR image was used as the Lum channel. I used Vicent's method to combine the Ha and R data. The method is beautifully demonstrated in Harry's tutorial.

Steve
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Offline dayers

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Re: Adding Ha to nebula image
« Reply #4 on: 2011 September 08 16:57:57 »
Hi Steve,

Thanks for your thoughts, and I will try using the HaR as Luminance. It seems there are a lot of ways to skin this particular cat!

Dave
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Offline Ioannis Ioannou

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Re: Adding Ha to nebula image
« Reply #5 on: 2011 September 09 11:50:05 »
HaR as L ? And how about G and B? A lot of people use this trick but destroys the other colors. Take a look on this http://pixinsight.com/forum/index.php?topic=2036.msg13106#msg13106

(although this Medusa is very good !! )
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Offline kerrywaz1

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Re: Adding Ha to nebula image
« Reply #6 on: 2011 September 19 14:46:36 »
I too am struggling with adding Ha to nebula images.

Could someone maybe please put together a brief tutorial on the best way to do this for those of us who are getting started with PixInsight and neophytes to using PixelMath?

Thanks,
Kerry
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Offline Silvercup

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Re: Adding Ha to nebula image
« Reply #7 on: 2011 September 26 13:11:20 »
Hi:

Perhaps you can try a HaRGB Combination script that I have developed.





The script is very simple to use:

 In Control Channels we choose the Ha and RGB images, the filters bandwidth and the Ha multiplication factor.

You will realize that lowering the RGB Bandwidth fewer Ha passes down and viceversa, but the differences are not very evident.

The multiplication factor is more  important because it will increase more or less the intensity of Ha, if we have a noisy channel we can not multiply much, if there is more signal we can increase multiply factor (in Harry's example up to 4) .

In Color Calibration Control we can choose whether or not to color calibrate the final image. Uncalibrated is selected by default for script to go faster. Checking Color calibration will calibrate the final image, for it, we will choose a preview of the background and a preview (or the entire RGB image) for white balance that you PREVIOUSLY defined in the RGB image. Depending on the image we choose Layers Structure detection or not. Finally, we can apply or not SCNR to green to finish calibration.

Checking AutoSTF we can apply an AutoSTF when we use a linear images, otherwise we would not see anything. In the case of combining with stretched images you must uncheck it.

Show Buttons. Show HaRGB and RGB buttons allow us to see the RGB and the HaRGB combination, both buttons open the console while working, do not touch the script until it closes the console and display the images, especially HaRGB Show takes a while, so don't be impatient as Pi can do strange things.

I put the script in a zip.

I would like to see results, and tell me if there is any fault, or if I can improve or what will happen.

Silvercup.

Edited again: Image Credits Jim Misti.
« Last Edit: 2011 September 26 13:28:25 by Silvercup »

Offline Nocturnal

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Re: Adding Ha to nebula image
« Reply #8 on: 2011 September 26 13:20:24 »
Looks really great silvercup! I like the results you're getting and also the GUI for the script looks really slick. One of the only scripts and processes I know with a preview -inside- the GUI. Nice.
Best,

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Offline Harry page

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Re: Adding Ha to nebula image
« Reply #9 on: 2011 September 26 13:37:02 »
Hi

This looks very interesting indeed  :laugh: a couple of questions for you

1) do we need to prepare the Ha image in any way
2) Are you adding the Ha to the red channel

Regards Harry
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Offline Silvercup

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Re: Adding Ha to nebula image
« Reply #10 on: 2011 September 26 13:46:29 »
Thanks Sander.

I only saw one problem adding Ha to the red channel, R channel "eats" G and B channels, althought you can recover with G and B saturation curves. So we must investigate a way to dim Red channel where you has G and B signal.

Harry, you only has to flatten Ha and RGB images with dbe if needed. The script do a linear fit between Red and Ha, then do the Vicent Peris pixelmath's with a little diference, in a third step the script do a max between original Ha  and recombined HaR. Yes, I add Ha to Red.

Silvercup.

Offline Harry page

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Re: Adding Ha to nebula image
« Reply #11 on: 2011 September 26 14:05:47 »
Hi

Thanks for the info All I need is some DATA to try this out

MAny thanks for your hard work


Regards Harry
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Offline sleshin

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Re: Adding Ha to nebula image
« Reply #12 on: 2011 September 26 16:12:43 »
Hi Silvercup,

Great idea for a script. Thanks for sharing it. Will give it a try.

Steve
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Offline Ioannis Ioannou

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Re: Adding Ha to nebula image
« Reply #13 on: 2011 September 27 00:42:10 »
Silvercup great job ! I also wanted to program something like this but time is always limited  :sad:
BTW, feature scripts -> Add does not add it , I guess it misses the Feature Id etc declarations ?
I can open it and run it with F9 though. I can't wait to go home and try it on older images.
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Offline cdavid

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Re: Adding Ha to nebula image
« Reply #14 on: 2011 October 10 17:55:57 »
also trying to load it using feature scripts.....it won't recognize it.  Any ideas?
Thanks
Carlos