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Stacking by Sequator 100 dng photos of night sky taken with a smartphone resulted in a (beautiful, I would say) populated star field where undesired arc strikes are seen all over the field. It is like as the program treated the vast majority of stars as wanted, while (perhaps the less brighter) others are just rendered as they moved along the 100 frames period.

Align stars was chosen then accumulation.

Is this a common problem using Sequator, or at least happened to some of you? Is there any trivial setting or way to redo the stacking? Thanks.

Attached is a compressed copy of the final photo. enter image description here

edit interested reader please follow at https://astronomy.stackexchange.com/questions/43689/streaks-on-a-stacked-star-field

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    \$\begingroup\$ Have you tried using a smaller subsets of images to see if the problem still exists? BTW, amazing results for a phone camera. \$\endgroup\$
    – qrk
    Commented May 5, 2021 at 20:14
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    \$\begingroup\$ was the phone handheld, or mounted on a tripod (or otherwise "still")? \$\endgroup\$
    – scottbb
    Commented May 5, 2021 at 20:25
  • \$\begingroup\$ @qrk good idea. Like input of 30 pics or so... \$\endgroup\$
    – Alchimista
    Commented May 5, 2021 at 20:39
  • \$\begingroup\$ @scottbb yes, though I cannot exclude some motion. Fact is that the result is satisfactory for the star indeed stacked. Do you have any mechanism in mind for which vibrations could result in the above strikes? Thanks. \$\endgroup\$
    – Alchimista
    Commented May 5, 2021 at 20:42
  • \$\begingroup\$ I wasn't thinking in terms of vibration. My mind was more leaning towards software working harder to stack unaligned images. \$\endgroup\$
    – scottbb
    Commented May 5, 2021 at 21:09

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The length of the arcs (compared to the very short trailing of the actual star images over each 30 second exposure) suggests that these are trails of actual moving objects.

Welcome to the Starlink era. While your phone isn't (yet) set up to use the Starlink network for communication, it appears it's well capable of detecting the satellites by their reflected light.

I can't be certain these are Starlink birds, of course -- but they're very numerous, in low enough orbits to move significantly in 30 seconds, and even the newer, "darker" ones reflect enough light to make them comparable in brightness to dimmer stars.

This kind of thing is why some astronomers have been complaining (since the second or third Starlink launch) that this network and its competitor(s) would be the end of ground-based astronomy, even as we approach the ability to build telescopes (or telescope networks) capable of resolving surface features on exoplanets.

Commenters have suggested (sensibly) that there are too many to be Starlink, and rather than criss-cross straight lines, these are arcs that seem to center around a point, so the other significant likelihood is that one or more of the exposures that were stacked contained rotation of the camera (phone), resulting in images the software couldn't merge with the others. If you can go through the images one by one, it should be very easy to spot the ones with long arcuate trails from among those with near-points (you might even be able to see the arcs well enough in large thumbnails, rather than have to open each file). Eliminate those files, and you should get an image without the arcs.

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    \$\begingroup\$ Way too many even for Starlink IMHO. And unless these shots are taken near 53° latitude, the tracks would criss-cross and not be all parallel (though for me they are more concentric than parallel). \$\endgroup\$
    – xenoid
    Commented May 6, 2021 at 11:56
  • \$\begingroup\$ Nice inspiration. Plus one for the originality anyway! Also to @xenoif. Latitude is 47° North. They also look concentric to me. But the criss cross link mention 72 orbital planes 22 satellite each. So in all cases we can say that the concerns of professionals is well motivated. Thank you both for the hints. \$\endgroup\$
    – Alchimista
    Commented May 6, 2021 at 12:10
  • \$\begingroup\$ A friend of mine just a smartphone photo with a beautiful train of what should be starlink. Besides the excitement of the first time, starlink really sucks.... \$\endgroup\$
    – Alchimista
    Commented May 7, 2021 at 19:26

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