Velocity component in a given direction due to the rotation
of the Galaxy.
R = sla_RVGALC (R2000, D2000)
J2000.0 mean (radians)
Component of dynamical LSR motion in direction
R2000,D2000 (km s-1)
Sign convention: the result is positive when the LSR
is receding from the given point on the sky.
The Local Standard of Rest used here is a point in the
vicinity of the Sun which is in a circular orbit around
the Galactic centre. Sometimes called the dynamical LSR,
it is not to be confused with a kinematical LSR, which
is the mean standard of rest of star catalogues or stellar
The dynamical LSR velocity due to Galactic rotation is assumed to
be 220 km s-1 towards , .