by Ann » Fri Jan 18, 2019 6:07 am
Hmmm. I'm a little disappointed.
The importance of star trail images is that they demonstrate that the Earth rotates about its axis. (Alternatively, of course, it might make some people believe that the Universe is rotating around us.)
(Yes, I know, some of these star trail images are pretty good at demonstrating the fact that stars are colored. Personally I prefer to find out about the color of stars by other means.)
North Celestial Pole. Note Polaris. Photographer unknown, sorry.
Otherwise, the only thing I really like about Celestial Pole star trails is that you can tell at a glance if you are looking at the North or the South Celestial Pole. That's because Polaris, the North Star, paints a brilliantly bright little arc right next to the "bulls-eye" of the star trails if we are looking at the North Celestial Pole.
So blotting out the Celestial Pole itself in an image like this robs us of the chance of telling right away which Celestial Pole we are looking at!
When I saw today's APOD, my thoughts went like this: Well, that's the South Celestial Pole, because Polares isn't there... wait a minute... surely all the other stars near the Pole can't be gone, too?
Ann
Hmmm. I'm a little disappointed.
The importance of star trail images is that they demonstrate that the Earth rotates about its axis. (Alternatively, of course, it might make some people believe that the Universe is rotating around us.) :wink:
(Yes, I know, some of these star trail images are pretty good at demonstrating the fact that stars are colored. Personally I prefer to find out about the color of stars by other means.)
[float=left][img2]http://burro.case.edu/Academics/Astr306_15/Coords/NMSkies_StarTrails2.jpg[/img2][c][size=85]North Celestial Pole. Note Polaris. Photographer unknown, sorry.[/size][/c][/float] [float=right][img2]https://upload.wikimedia.org/wikipedia/commons/thumb/e/e5/All_In_A_Spin_Star_trail.jpg/1280px-All_In_A_Spin_Star_trail.jpg[/img2][c][size=85]South Celestial Pole.
A. Duro/ESO - http://www.eso.org/public/images/potw1631a/[/size][/c][/float]
Otherwise, the only thing I really like about Celestial Pole star trails is that you can tell at a glance if you are looking at the North or the South Celestial Pole. That's because Polaris, the North Star, paints a brilliantly bright little arc right next to the "bulls-eye" of the star trails if we are looking at the North Celestial Pole.
So blotting out the Celestial Pole itself in an image like this robs us of the chance of telling right away which Celestial Pole we are looking at! :evil:
When I saw today's APOD, my thoughts went like this: Well, that's the South Celestial Pole, because Polares isn't there... wait a minute... surely all the other stars near the Pole can't be gone, too?
Ann