Re: starship-design: Massively Distributed Computing for SETI

[Steve VanDevender <stevev@efn.org>]

Ben Franchuk writes:
 > "L. Parker" wrote:
 > > It all depends upon which star you choose, some do display quite a bit of
 > > proper motion relative to us. However, you are correct, that most do not, IF
 > > you average for the effects of our own planetary orbit
 > .
 > Does anybody know of any programs that do that, showing positions of the stars
 > in the past or the future from any point in space?

Any good astronomical ephemeris program should do that, for the stars
whose proper motions are known.  There's a very nice program called
XEphem that runs on UNIX systems.

Also, Lee, proper motion is defined as a star's average angular motion
against the sky over a multi-year period, not any instaneous measurement
of relative velocity.  In general the proper motion of a star has to be
determined by observations of a star's movement over long periods,
subtracting out various things like relativistic aberration, parallax,
and other short-term variations in the star's apparent position.