RE: Heliocentric julian date adjustment

[aah@nofs.navy.mil]

>Over what time period would the barycentric julian date change, and by how
>much?  If you can point to some software (or, gasp, equations) which does
>the conversion, I'll give it a go, converting into Perl.
  Barycentric refers to the center of mass of the solar system, a point
slightly above the surface of the sun when Jupiter and Saturn are on the
same side.  The correction between heliocentric and barycentric is
then primarily an annual change, much like heliocentric, since it
depends on the relationship between the solar system center and the
earth's orbit around the sun.  There is a longer term variation that
relates to the orbital period of Jupiter and Saturn, of course.
Personally, I'd ignore the extra complexity of barycentric correction
since it is less than any reasonable exposure time for TASS, and
very few people report BJD anyway.  Most of the time when truely accurate
time is important (campaigns with satellites for example), the observations
are done nearly simultaneous and any HJD->BJD correction is the same
for all observations.  The main place I've seen BJD used is for
pulsar timing.   If you are really interested, Look up barycentric or
barocentric under google to find references;  I don't know of a
publically available piece of software that does the correction.
Arne