Can't tell if this red is artifact or is really there...

Processing Deep Sky Galaxy Artifacts
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Harry Karamitsos avatar
Harry Karamitsos avatar
I processed my image of the Markarian's chain in HaLRBG. 



Markarian's chain in HaLRBG

I get this weird red area between the galaxies. Its not clear to me if this is real or artifact.  I don't see it in any other images of the Markarian's chain so I suspect it is artifact...

I did a linear fit using green as the primary and it is still there. I tried a number of different gradient removal tools and none work. Im not sure what else to do.

This is the RGB image after Linear fit and RGB combination using red as the primary...

RGB_after_Linearfit.jpg

There are all these read and green blotches. I tried the new Multiscale gradient correction but that part of the sky  doesn't seem to be in the database...

Any ideas?
John Hayes avatar
John Hayes avatar
That is most likely a processing artifact.  How did you add the Ha signal to the LRGB data?  Did you remove the continuum before combining?

John
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Markice Stephenson avatar
Markice Stephenson avatar
I would bet on most of this being accurate. Here's the deepest image that I have seen of that region of the sky: https://www.rc-astro.com/photo/id1245.html

You can also search Markarian's Chain in the advanced search here on astrobin and sort by integration time/bortle scale/etc., which will help you find the deepest images of the objects that you are looking to compare. 

Here are some comparable images that share similar structure to your image:
Img 1
Img 2
Img 3

So, it's clear that at least some of the what you're seeing is accurate. When overstretching, lots of weird things can happen and you can introduce artifacts, but this looks fine. You'll have to obviously go pretty deep to define the structures that you are seeing though

Hope this helps,

Kice
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andrea tasselli avatar
andrea tasselli avatar
It's an artifact compounded by some faint signal in Ha over there (or rather between there and here). You stretched the background way too much and it's not balanced. You should see first some Ha connected to M84/M86 and I can't see that.
Scott Badger avatar
Scott Badger avatar
Using linear fit on the color channels before combining them isn’t recommended. I’d think color calibrating would negate the linear fit though, so not sure it’s a factor here.

Cheers,
Scott
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