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LRBG combo fail?

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#1 Star Slinger

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Posted 08 April 2020 - 11:51 PM

I’m learning how to combine channels. Last night I acquired 150 lights, 100 darks, and 50 each of RBG all of which were 10 sec subs. I went through my post processing ritual and was almost done. Went to combine the Lum with the RGB data and the result that popped out was dark. Almost black with hints of dark red *see attached pic*. Super frustrating after spending hours processing only for final result to be unusable. I’m not certain what I’m doing wrong, or perhaps even forgetting. Has anyone else experienced this before? 
 

I ended up just saving the RGB data and calling it good since it was colorful and looked nicer than the Lum. Help! bawling.gif

Attached Thumbnails

  • CB858091-D63B-475D-9052-C014A3A79CC5.jpeg
  • 956D2E3C-0439-4248-B78E-4B09FDEB2177.jpeg

Edited by Star Slinger, 09 April 2020 - 08:57 AM.


#2 44maurer

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Posted 09 April 2020 - 12:22 AM

No attached pix.

 

you need to include a lot more info on equipment used and settings.

 

at 50x10 second subs, you didn’t gather much information, and I’m assuming you are saying 150 subs of 10 seconds for lum. Again, not much data.

 

without knowing the additional information, it’s hard to help, but you should measure Total exposure time in hours, not minutes and singles exposure time in minutes, not seconds.



#3 Star Slinger

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Posted 09 April 2020 - 08:37 AM

I know, this probably wasn’t enough data but after 10 seconds the subs were blurry. I’ve been having one heck of a time getting focused lately and it takes my entire night. I have a Rigel nStep but no clue how to set it up initially. In any case, thank you perhaps I just need longer subs. Pic is now attached. 

 

Oh and I’m using my ED80 and ASI1600 and processing in PI. 

 

 


Edited by Star Slinger, 09 April 2020 - 09:16 AM.


#4 Madratter

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Posted 09 April 2020 - 08:42 AM

Had you already stretched your RGB data? Had you already stretched the L data?



#5 Star Slinger

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Posted 09 April 2020 - 08:57 AM

Yes I stretched them all. 



#6 Madratter

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Posted 09 April 2020 - 09:41 AM

Assuming those stretched versions looked good, try this.

 

Do a ChannelExtraction on your stretched RGB stack. Select CIE L*a*b* mode. You should get three result images. One of them will be the luminosity portion of the RGB stack. Throw it away. That will leave you with the a and b channels.

 

Then do a Channel Combination. Again select CIE L*a*b*. This time use your stretched L stack for the L portion. Use the a and b channels you just extracted for your a and b channels.

 

Assuming your L stack and RGB stacks look good to start with, this should give you at least an OK result. If you stretched your L data too much compared to the stretch of the RGB data, you may lose color saturation. But try this and see what occurs.


Edited by Madratter, 09 April 2020 - 09:48 AM.

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#7 44maurer

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Posted 09 April 2020 - 10:39 AM

I know, this probably wasn’t enough data but after 10 seconds the subs were blurry. I’ve been having one heck of a time getting focused lately and it takes my entire night. I have a Rigel nStep but no clue how to set it up initially. In any case, thank you perhaps I just need longer subs. Pic is now attached. 

 

Oh and I’m using my ED80 and ASI1600 and processing in PI. 

What gain and offset are you using? For 10 seconds, those pix don’t look too bad. 
 

when you were shooting, where was your histogram? I shoot for the histogram to be just off the left side, look at a few of the brighter stars to make sure you aren’t clipping them, it’s okay to clip of few when you have some really bright stars on the image.



#8 Alex McConahay

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Posted 09 April 2020 - 02:08 PM

Call up each of the masters, and put your cursor on the same points in each frame (try two or three samples). Go for background. 

 

Look to the bottom of the workspace, and read off what the  K setting is---All four should be about equal. Not precisely, maybe, but somewhat close. If not, you may need a Linear Fit before attempting to combine. Call the Linear Fit process, make the strongest channel (the one with the highest "K" reading) your master, and drag the new instance to each of the other three. 

 

Then do the LRGB combine.

 

That may help.

 

Alex




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