Most wobbly little telescopes are refractors and the diagonals can also get pretty dirty. I have seen, in small low magnification instruments, bats at several hundred feet darting around in the sky and backlit by the moon.Ive never seen them against Jupiter. Hope that helps,......
So far, no one has seen anything that crosses Jupiter in a second, although I have seen satellites cross over galaxies many times and if one were bright enough one might see one cross in front of Jupiter, but this would be rare. In inexpensive telescopes on poor mounts I've seen all kinds of weird effects.
Another source of dust spots is on the diagonal of the instrument. Most wobbly little telescopes are refractors and the diagonals can also get pretty dirty.
I have seen, in small low magnification instruments, bats at several hundred feet darting around in the sky and backlit by the moon. I've never seen them against Jupiter.
Hope that helps,
GN
Whatever you saw, it wasn't Jupiter and the Red Spot, or a moon. My guess is that you had a really high magnification on, and you were looking at a star or planet that was way out of focus. Assuming your telescope was a reflector, the black spot was the out-of-focus secondary mirror, and the motion was turbulence in Earth's atmosphere.
No moon will orbit a planet at that speed. At that speed the moon would just go flying off into space. I don't know what you saw, but it definitely was not a moon orbiting a planet.
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That kind of speed sounds really unlikely. Maybe it was an artificial satellite going around the Earth, or an asteroid?
You seem to have misinterpreted what you've seen.
That's no moon.
