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How to get rid of satellite trails

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I had stacked a set of images the other day and found that a satellite trail was just visible in the final output. I sorted through the subframes and found the offending frame. I was pushed for time and didn't want to do a restack, so I was just about to tackle it with the clone tool and I suddenly had a brainwave. I rotated the stacked image noting how many degrees I had rotated it by until the trail was vertical. Then I used Noel Carboni's vertical banding removal tool in Photoshop to remove the line. I then rotated the picture back the same number of degrees and voila no trail visible at all.

Now you can use the frames you usually chuck away and recover some of the exposure time.



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Or, use Ray Gralak's Sigma (http://www.gralak.com/Sigma/) to do the stacking and perform a sigma clipped average on the aligned images. I use it for all my combining of images.

It offers the S/N of an average with the noise rejection of a median combine (straight average combines always have higher S-N ratios than a straight median). It works by rejecting individual pixel values that fall outside of a user defined range (it uses the term "sigma" from the calculated standard deviation of each individual pixel value).

It works best with 10 or more images (so the standard deviation is more accurately calculated, and so any rejected values don't massively lower the S-N ratio), and it works on satellites/cosimc ray hits/hot pixels (largely - it's not perfect and it takes a bit of fiddling to get the right settings) by rejecting the pixels in the trail as being outside of the accepted range about the average value (too bright). Really handy if you can dither your subs too, as most of the hot pixels that remain after dark subtraction then disappear.

Check out the site - it's excellent, and even better, it's free.


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I'll take a look at that. There are various stacking options in DSS that perform the stack in different ways, some of them get rid of trails anyway.

Its the planes that do my head in. I've had several 5 min subs ruined by a low flying plane putting a ladder mark all over the pic

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