I haven't used
Celestia in ages and rather than go and install it in order to give a quick answer, I'm going to be terrible and go by memory. My recollection is that it gives you apparent coordinates of any selected target wherever in space you move yourself – at least in some coordinate system that is. You only need to go around another star to view the sky from its perspective and pick other star's coordinates.
If you want a more hands-on approach with more control on the input data, you only need a catalogue of stellar positions in 3D (right ascension, declination, distance) and some coordinate transformations to move from a solar centric coordinate system to one centered around another star. Here's how you should do it:
- Transform the stellar positions from the original spherical coordinates (RA, dec, d) to Cartesian coordinates (x, y, z). The required formulae are found here.
- Move these coordinates so that the origin now coincides with your chosen star. This simply means subtracting your star's (x, y, z) coordinates from every single star in the list.
- Transform back from the shifted Cartesian coordinates (x', y', z') to new spherical coordinates to find out the positions of the stars on this alien sky. The required formulae are here.
If you want that the celestial coordinate system around the star is oriented in any other way than how ours is on Earth, you'll need to add an additional
rotation of the coordinates to that procedure. That's, however, not necessary if you only want to see how the sky looks like from another star.
The old standard catalogue for stellar positions is the Hipparcos catalogue:
http://vizier.u-strasbg.fr/viz-bin/Vizi ... I/311/hip2. This is already somewhat old and new superior data is at the moment being gathered by the Gaia mission:
http://gea.esac.esa.int/archive/. It's current data release isn't nearly the final one, but already this partial data produces more accurate output than what Hipparcos was capable of. Gaia's main drawback right now is that it doesn't include all the brightest stars yet due to the difficulty of measuring accurate positions of very bright sources. These require more data to derive accurate distances and will be added in the future data releases.
If you decide to go with the hands-on route, you'll notice that the astrometric catalogues like Hipparcos and Gaia don't give distances directly, but instead report the directly measured
parallax, in these cases in the units of milliarcseconds. You'll need to invert these into distances yourself. If the parallaxes
plx are given in milliarcseconds, the formula
d = 1000/plx will give you estimated distances in parsecs. For smaller distances the errors in parallax remain quite small, but if you move too far from the Sun, they will eventually become comparable with the actual values of the parallax measurement. This means that larger astronomical distances always have disproportionately large error bars. That's something you need to remember if you want to simulate the night sky around a very distant star.
I realize that this answer won't be too useful for a whole lot of people, but I hope it's at least helpful to see some of the background that goes into determining stellar positions in space and on the sky.