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Does "stacking" also mean "aligning"?

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#1 crb02l

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Posted 15 May 2019 - 04:19 PM

So I'm just starting to image and trying to learn as much as I can before I take the next steps. Relative, to stacking images, does this mean every picture you use DSI or Registax to stack must be exactly the same in terms of size, where stars are located within the frame?

 

In essence, if the stars have shifted a little in one frame to another, does the software adjust to put the stars over the stars so they are aligned properly? 

 

Hope this makes sense. And yes, I'm starting to read all the good books I see folks recommending. Thank you so much.

 

 



#2 wrvond

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Posted 15 May 2019 - 04:28 PM

It's my understanding the software aligns the images, but only within certain limits.



#3 bobzeq25

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Posted 15 May 2019 - 04:29 PM

So I'm just starting to image and trying to learn as much as I can before I take the next steps. Relative, to stacking images, does this mean every picture you use DSI or Registax to stack must be exactly the same in terms of size, where stars are located within the frame?

 

In essence, if the stars have shifted a little in one frame to another, does the software adjust to put the stars over the stars so they are aligned properly? 

 

Hope this makes sense. And yes, I'm starting to read all the good books I see folks recommending. Thank you so much.

There are two processes, aligning the stars by shifting the subexposures positions, and stacking the data.  With some software, operated in certain ways, those are handled by the software in one operation setup by you.  Other software, when you use other methods, may have you performing two operations.

 

You'll find some people recommending PixInsight, a complicated program.  One of its strengths is that it can align and stack most anything, even subexposures from different cameras that are different sizes and twisted with regard to each other.

 

But it's a difficult program to learn, there are easier, that can handle a large majority of the situations you'll encounter.


Edited by bobzeq25, 15 May 2019 - 04:32 PM.


#4 OldManSky

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Posted 15 May 2019 - 04:30 PM

Well...no.

They're two different things.

Aligning means figuring out how far off in translation (x and y movement) and rotation one image is from another.

Stacking means combining the pixel values of images (two or more) to produce a new image whose pixels are some function of the pixels in the "stack" of source images.

 

In the actual work of processing images, those two different things are often done in one "batch" process.  But you can't "stack" until all of the images in the stack are aligned, so alignment is always done first, then stacking.  Even if the software you use sort of hides that from you.



#5 2ghouls

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Posted 15 May 2019 - 04:33 PM

Most astronomy specific software will handle both alignment (also known as registration) and stacking (aka integration) of your images. Like Bob said, some programs will seem to combine the processes (DSS for example), but as OldManSky points out they are really two different things.



#6 crb02l

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Posted 15 May 2019 - 05:42 PM

Thank you folks, You are great.



#7 kathyastro

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Posted 15 May 2019 - 06:08 PM

And, in practice, "stacking" of DSO images at least (i.e. DSS, not Registax) includes calibration.  Calibration is done first, then registration, then integration.




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