Stacking versus mos...
 
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Stacking versus mosaic


(@tak)
Molecular Cloud Customer
Joined: 2 years ago
Posts: 4
Topic starter  

It is my understanding that stacking reduces noise and enhances signal.  Does mosaic mode do the same?  Or is mosaic mode just about alignment?  I ask because I have sessions with more 60% overlap and would like to take advantage of signal to noise enhancement.  If I process each session and then load the final products into mosaic mode will the mosaic image processing take advantage of stacking overlap regions to reduce noise?  Also - do people load final products of individual sessions as un-stretched or stretched FITS files?  Thank you!


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(@wvreeven)
Galaxy Admin
Joined: 4 years ago
Posts: 2035
 

@tak It depends 🙂 If you load all raw subs of a mosaic and integrate them all together in mosaic mode, APP will integrate the subs of each panel. If you integrate the panels first and then load them to create a mosaic, APP will have applied stacking on each individual panel.


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(@tak)
Molecular Cloud Customer
Joined: 2 years ago
Posts: 4
Topic starter  

It sounds like I can only take advantage of stacking once.  In this case I have a question about integrating my overlapping frames together.  When I try to pick a reference frame I receive an error telling me I must star analyze first but I have already completed the analyze stars step.  I can not get past this.  A person wrote about a similar problem in this forum but they were using a mono camera and I did not understand the suggested work around.  I am using a ZWO 294MC Pro. Thank you.


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(@wvreeven)
Galaxy Admin
Joined: 4 years ago
Posts: 2035
 
Posted by: @tak

It sounds like I can only take advantage of stacking once.

Well, stacking only works if there is overlap, which is the case when processing the raw images. In general a mosaic will have frames with at most about 20% so there stacking won't help much. But when creating the mosaic, APP will reduce the noise there where the images overlap. For what it is worth, this is the case for all image stacking applications because they all need many images for the same area of the sky to be able to reduce noise.

Posted by: @tak

When I try to pick a reference frame I receive an error telling me I must star analyze first but I have already completed the analyze stars step.

APP will choose a reference frame for you so there is no need to select one yourself. The simplest way of processing the images is to load all in tab 1 into one session and then to go straight to tab 6 and hit the integrate button. APP will sort it all out for you and will perform all intermediate steps automatically. Can you confirm that that works for your raw images?


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(@tak)
Molecular Cloud Customer
Joined: 2 years ago
Posts: 4
Topic starter  

Does it automatically choose the correct reference frame?  Two sessions may have frame with no overlap but a third session has overlap with both.  Will APP automatically pick the third session for the master registration frame?


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(@wvreeven)
Galaxy Admin
Joined: 4 years ago
Posts: 2035
 

@tak APP chooses a reference frame based on star shapes and background levels, to name a few. It doesn't necessarily choose one that all others have overlap with.

In case some frames don't have overlap with each other then you'll need to process in mosaic mode. 


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(@tak)
Molecular Cloud Customer
Joined: 2 years ago
Posts: 4
Topic starter  

Thank you for your help Wouter.


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