[fitswcs] LSR in Paper III

[Patrick Wallace]

On Tue, 25 Jan 2005, Arnold Rots wrote:

> Working on Space-Time and spectral coordinate metadata in the VO
> context, I took a harder look at Table 12 and noticed that the
> magnitudes for LSRK and LSRD were quoted from Delhaye (1965) as 20,
> respectively 16.6 km/s.  Yet, Delhaye gives values of 19.5 and 16.6.
> Where does the difference come from?

In the SLALIB routine sla_RVLSRK I quote Delhaye (1965) for its
description of what the different LSRs mean but then give a velocity of 20
km/s towards RA 18h Dec +30d (1900) that is taken from Methods of
Experimental Physics, ed Meeks, vol 12, part C, sec 6.1.5.2, p281.  I
think the reason was that this corresponded to what people were using in
practice.

Delhaye (1965) is also quoted for the dynamical LSR routine sla_RVLSRD,
but this time the numerical values are from that reference.  The vector is
(+9,+12,+7) km/s in Galactic coordinates, and the 16.6 km/s figure is the
approximate magnitude of this vector.


Patrick Wallace
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