<p>I have taken photos at different exposures from different places of the Orion constellation. I wish to find the effect of skyglow on the limiting magnitude of stars in the Orion constellation. How can I estimate the limiting value of any star from its RGB pixel value in the photograph?</p>

CC BY-SA 3.0
2017-01-18T06:09:48.923Z
What image analysis software are you using? There are quick easy tricks if you're using something like DS9 (it's free), but it could be MUCH more difficult using something like ... MSpaint.
LaserYeti
CC BY-SA 3.0
2017-01-18T07:16:45.790Z
The files that I am working with are in NEF format. DS9 doesn't seem to support NEF, or even JPG, for that matter.
Shashank Acharya
CC BY-SA 3.0
2017-01-18T13:49:42.053Z
Try converting to something DS9 can use. Astronomers tend to use FITS file format and I'm sure you can find some free software to do this. NEF and JPG are not good choices for image analysis.
zephyr
CC BY-SA 3.0
2017-01-18T14:21:56.237Z
Seems I answered this very question a day or two ago, but I can't remember in which SE site :-(
Carl Witthoft
CC BY-SA 3.0
2017-01-19T05:51:48.400Z
With DS9, you can open any GIF, JPEG, TIFF, PNG, PPM, using the "File" - "Open Other" - "Open Photo". Granted, on my windows machine this crashes DS9 every time, with anything other than a FITS file, but it works like a charm on my Linux machine. Not too sure about NEF files though. I just broke my wife's nikon, otherwise I'd check it out. Either way, I'd suggest converting the files, or finding another analysis tool. Sorry.
LaserYeti
<photography><photometry><light-pollution>
Convert RGB pixel value of an image to limiting magnitude
Shashank Acharya
# Convert RGB pixel value of an image to limiting magnitude

(Asked by: username_0 on 2017-01-18)

I have taken photos at different exposures from different places of the Orion constellation. I wish to find the effect of skyglow on the limiting magnitude of stars in the Orion constellation. How can I estimate the limiting value of any star from its RGB pixel value in the photograph?

**Tags:** photography, photometry, light-pollution

> **Comments:**
> **username_1**: What image analysis software are you using? There are quick easy tricks if you're using something like DS9 (it's free), but it could be MUCH more difficult using something like ... MSpaint.  
> **username_0**: The files that I am working with are in NEF format. DS9 doesn't seem to support NEF, or even JPG, for that matter.  
> **username_2**: Try converting to something DS9 can use. Astronomers tend to use FITS file format and I'm sure you can find some free software to do this. NEF and JPG are not good choices for image analysis.  
> **username_3**: Seems I answered this very question a day or two ago, but I can't remember in which SE site :-(  
> **username_1**: With DS9, you can open any GIF, JPEG, TIFF, PNG, PPM, using the "File" - "Open Other" - "Open Photo". Granted, on my windows machine this crashes DS9 every time, with anything other than a FITS file, but it works like a charm on my Linux machine. Not too sure about NEF files though. I just broke my wife's nikon, otherwise I'd check it out. Either way, I'd suggest converting the files, or finding another analysis tool. Sorry.  

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## 0 answers

