by geckzilla » Thu Apr 03, 2014 10:53 pm
Astro Quake wrote:While comparing the images that geckzilla kindly shared, one of the stars (upper right corner, about 1 o'clock) appears to be in a different position!
Is this a known phenomena or an optical illusion of some kind?
A little of both. I'd guess at least one is a cosmic ray hit which just happens to be sort of near a real star or another cosmic ray hit in the other image. I don't see any real stars moving, though it does happen quite a lot when you have two images of the same thing a few years apart.
Parallax can cause nearby stars to look as if they are moving even over short periods of time, say while the telescope is on one side of the earth and then moving to the opposite side. Other than that, stars
do move. Neither of those are happening noticeably in the blink image, though.
It's funny, because the specks of cosmic rays which are completely and utterly mundane, boring things, but when you don't know what they are they seem mysterious and exciting. They're just a confusing nuisance. The vast majority of them are cleaned off the images but sometimes they sneak in if they are small or look enough like a star.
[quote="Astro Quake"]While comparing the images that geckzilla kindly shared, one of the stars (upper right corner, about 1 o'clock) appears to be in a different position!
Is this a known phenomena or an optical illusion of some kind?[/quote]
A little of both. I'd guess at least one is a cosmic ray hit which just happens to be sort of near a real star or another cosmic ray hit in the other image. I don't see any real stars moving, though it does happen quite a lot when you have two images of the same thing a few years apart. [url=https://en.wikipedia.org/wiki/Parallax]Parallax[/url] can cause nearby stars to look as if they are moving even over short periods of time, say while the telescope is on one side of the earth and then moving to the opposite side. Other than that, stars [url=https://en.wikipedia.org/wiki/Proper_motion]do move[/url]. Neither of those are happening noticeably in the blink image, though.
It's funny, because the specks of cosmic rays which are completely and utterly mundane, boring things, but when you don't know what they are they seem mysterious and exciting. They're just a confusing nuisance. The vast majority of them are cleaned off the images but sometimes they sneak in if they are small or look enough like a star.