Author Topic: Problems doing Harry's Ha + RGB tutorial result  (Read 1186 times)

Offline helgeras

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Problems doing Harry's Ha + RGB tutorial result
« on: 2014 May 04 14:29:04 »
Hi,
I am trying to add a Ha image to a RGB image.
I have both images linear and try to apply the formula
  ((Ha * 100 ) - (RGB * 12)) / (100 - 12)
with rescaling turned off as described in the tutorial.
The result of this is a nearly totally black image even after stretching.
What am I doing wrong here?

Should I somehow normalize the images before doing the above?

Here are the images I use:
The R image: https://dl.dropboxusercontent.com/u/7714699/RGB_Work_R.fit
The Ha image: https://dl.dropboxusercontent.com/u/7714699/RGB_Work_Ha.fit
The result: https://dl.dropboxusercontent.com/u/7714699/RGB_Work_Result.fit

Thanks for any help you can give,
Helge

Offline Rob Friefeld

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Re: Problems doing Harry's Ha + RGB tutorial result
« Reply #1 on: 2014 May 09 21:06:10 »
No replies, I see, so I thought I would tell you that I at least looked at your images, but I don't know the solution.
I did get the same result you did using the script. This script has worked for me in the past.

I tried doing a linear fit on the images before applying the script, and the result was bizarre--the galaxy looked like a black hole. Hmm. I tried changing the "-" in the formula to a "+" and the result looked like an average of the two input images.

There does seem to be something funny about the data. Were these images acquired in the same format? I'm mystified, too.

Offline oldwexi

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Re: Problems doing Harry's Ha + RGB tutorial result
« Reply #2 on: 2014 May 10 03:39:47 »
Helge,
Your file RGB_R_Work is not a RGB Image it is a gray monochrome Image. (Looks like a Luminance)
Your Ha file is 25 times less bright than your so called R File. So linear fit is needed also.
Start Statistics and look at the mean or median value to check this.

Usually i use a splitted RGB Image and mix with your formula the R with the Ha
and Keep the green and blue channel as they are.
In the R channel your formula
in the G channel $T
in the B channel $T

Dont forget to uncheck the "Use a single RGB Expression"

Gerald

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Re: Problems doing Harry's Ha + RGB tutorial result
« Reply #3 on: 2014 May 10 06:36:21 »
Hi

Sorry I missed this  :-[ , But it looks like the "master" has sorted it

Harry
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