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by
jarmo
Is this comet or asteroid or what?
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by
CTidwell3
Its an artifact. Comets and asteroids move in a straight line. You can see that this moves up between frame 1 and 2, down and right between 2 and 3, then back left between 3 and 4. This motion happens because each time a picture is taken, the telescope is aimed just slightly off from where it was aimed when the previous picture was take.
So, for example, if there was dust on a lens or a hot pixel on the ccd in frame one, by aiming slightly higher, that dust or hot-pixel will be at the same location on the image, but at a different place when compared to the background stars. Then when the images are aligned so that the stars do not move between images, artifact like these appear to move up.
By aiming the telescope in this way in a non-linear pattern, artifacts move in a non-linear pattern, allowing anything that does not move in a straight line between frames to be ruled out as an actual celestial object.
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