[fitswcs] LSR in Paper III

[Arnold Rots]

Amusing, Delhaye was inconsistent.
However, are we sure 20 km/s is/was general practice?
For one thing, I have a vague recollection that the old Lund tables,
which I suppose were in use till the mid-60s, were based on 19.5.
Would a poll be appropriate?

On a different note:
ZOPT is defined.  In principle one could allow for ZRAD and ZELO,
defining Vxxx = c . Zxxx.
I don't know whether it's useful, but it would make things completely
general.

  - Arnold

Patrick Wallace wrote:
> 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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Arnold H. Rots                                Chandra X-ray Science Center
Smithsonian Astrophysical Observatory                tel:  +1 617 496 7701
60 Garden Street, MS 67                              fax:  +1 617 495 7356
Cambridge, MA 02138                             arots at head.cfa.harvard.edu
USA                                     http://hea-www.harvard.edu/~arots/
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