Question about clou...
 
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Question about clouds


(@tbarn)
Brown Dwarf Customer
Joined: 5 months ago
Posts: 11
Topic starter  

Should I manually remove light frames that have cloud coverage prior to running an APP session?

And if so, how aggressively? If a few wisps of clouds are visible, should I include or remove those lights?

And how about airplanes? Does it make sense to remove those frames, too?

This topic was modified 4 months ago by Tom Barns

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(@wvreeven)
Galaxy Admin
Joined: 4 years ago
Posts: 1647
 

@tbarn Tom, obviously clouds negatively influence the integration result so it is much better to use as few frames with clouds as possible. The same applies to airplanes, meteors, satellites and other transient phenomenons. Having said that, it is also clear that not all of us have the luxury to keep on shooting and shooting images until all are perfect.

Regarding clouds, APP analyzes each frame and assigns a quality score to them depending on the shape of the stars and the signal to noise ratio of the stars with the background. Based on the quality scores, it applies more or less of the frames to the final image. If the star shapes are good but the SNR low then it may still decide to use the star data for more intense star colors for example. On top of that, in tab 6 you can select if APP should stack all images or a percentage smaller than 100 of them. It is up to you to select what percentage to stack.

Regarding airplanes, meteors, satellites and other transient phenomenons, APP determines in each frame what signal corresponds to that found in other frames and uses a technology called sigma clipping to get rid of transient phenomenons. Here, the more frames you have, the better because that way APP can much better build up statistics of the frames and decide what to include and what not. If you see that APP didn't get rid of all airplane signal then you can play with the outlier rejection parameters in tab 6.


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(@wvreeven)
Galaxy Admin
Joined: 4 years ago
Posts: 1647
 

@tbarn Adding to this, after APP has performed step 5, Normalize, you can sort the frames by sky background and create an analytical chart of the sky background. You can then easily identify the frames with clouds and discart those. 


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