projection on earth's surface?

Question

assume that somebody is standing in a place during a starry night and looking straight up sees a star.another one 100mls away sees another star over his head and a third one 200mls away at another direction does the same.the three stars makes a triangle on the skymap whose projection on earth's surface is our three people.that's exactly what i want too see.a triangle on earth's surface.can any body suggest me a software that does this exactly?

Answer 1

Well, the best I can suggest is software used for telescopes. This software enables you to input the location of a person on Earth and then allows you to see what's available to you from that location at specific moments in time. So if Person A is looking straight up and picks the star directly overhead, and Person B, say 1000 miles away at the exact same time looks straight up, they will see a different star (but will be able to look about 5 degrees towards Person A to see their star). And the Person C, at the same time can do the same in another location.

Using a telescope charting software (there are many) you can input your location and date/time and it can provide you a map of the stars overhead and you can look for the star closest to straight up.

If you are looking for a triangle, you might just use the constellation Cassiopia. (winter constellation in the USA). The full set of stars in it makes a "W" shape, but the last two points in the W are fainter and not as evenly spaced, so three of the stars really stand out and make what looks to be a perfect triangle. I believe the constellation is supposed to be a "throne", but I've forgotten some of the mythology around it.

Have fun!

Answer 2

If I'm understanding you correctly, you want a view of the stars as they would look from *outside* the celestial sphere.

The celestial sphere is the imaginary sphere that all the stars appear to be on (of course they aren't, they are all at different distances from us). A planetarium is a large version of a celestial sphere model (half of the sphere, of course). You can buy hand-held models which are justs balls with the stars painted on them. Old star atlases (circa 1600, 1700 or so) actually drew the stars as they would be seen from outside the celestial sphere, kinda like God's view of the stars.

Unfortunately, I don't know of any software that does this, since most software is made for people who want to see the stars from their own back yards. But if this is what you want, perhaps now you can ask the question again and more people will understand, and be able to help, you.

Ask this: "Is there any software that will give a view of the celestial sphere from the outside of the celestial sphere?"

Some links about celestial spheres:
http://www.sciencefirst.com/vw_prdct_mdl.asp?prdct_mdl_cd=CG616
http://www.nationalgallery.org.uk/collection/features/science/globe.htm
http://en.wikipedia.org/wiki/Celestial_sphere