by NoelC » Thu Mar 27, 2008 11:52 am
We cannot resolve stars into disks (well, just a few really close, big ones, but not with amateur equipment and not at this relatively low focal length). No matter how oblong a star may actually be you wouldn't see it as ovoid in an image like this.
The disks you see in images such as this one are from the relatively bright point light sources (stars) essentially overwhelming the imaging equipment, due to the light diffracting around the edges of the optics and also to some extent spilling over to adjacent photosites on the imager itself.
What you're seeing is really two stars of similar apparent brightness that appear very close together (though they may be a huge distance apart in actuality). Note the following image from the Digitized Sky Survey, with 1 arc-second per pixel resolution. You can better see it's a close double here.
Oh, and stars DO move - it's called "proper motion", but you wouldn't detect it in an exposure this short. You can actually see the proper motion of many stars due to their changed positions when carefully comparing exposures taken many years apart.
-Noel
We cannot resolve stars into disks (well, just a few really close, big ones, but not with amateur equipment and not at this relatively low focal length). No matter how oblong a star may actually be you wouldn't see it as ovoid in an image like this.
The disks you see in images such as this one are from the relatively bright point light sources (stars) essentially overwhelming the imaging equipment, due to the light diffracting around the edges of the optics and also to some extent spilling over to adjacent photosites on the imager itself.
What you're seeing is really two stars of similar apparent brightness that appear very close together (though they may be a huge distance apart in actuality). Note the following image from the Digitized Sky Survey, with 1 arc-second per pixel resolution. You can better see it's a close double here.
[img]http://forum.ourdarkskies.com/gallery_images/1204938574/gallery_131_16_27404.jpg[/img]
Oh, and stars DO move - it's called "proper motion", but you wouldn't detect it in an exposure this short. You can actually see the proper motion of many stars due to their changed positions when carefully comparing exposures taken many years apart.
-Noel