./toolbox
chdoppler.pro

Last modification date:

Sun Oct 22 03:20:02 2017

chdoppler

function chdoppler(ra, dec, julday, [obspos=double [2]], [/light])

computes the projected velocity of the telescope wrt six coordinate systems: geo, helio, bary, lsrk, lsrd, gal negative velocities mean approach The standard LSR is defined as follows: the sun moves at 20.0 km/s toward ra=18.0h, dec=30.0 deg in 1900 epoch coords Fully vectorized. All three arguments must have the same dimensions.

This code came via e-mail from Carl Heiles via Tom Bania on 11/04/2004. Updated using code found via google from same source on 11/30/2009. Local changes:

• modify this documentation for use by idldoc.
• removed path argument and related code, replaced by obspos argument.
• default position is the GBT.
• Observatory longitude was not being passed to juldaytolmst.
• LSRD added
• Galactocentric added
• Checked against aips++ Measures. Differences were less then 20 m/s in one test case (less then 10m/s for geo, bary, and lsrk).
• Double precision throughout.
• Relativistic addition of velocities.

Returns

The velocity in km/s, or as a faction of c if the keyword /light is specified. the result is a 6-element vector whose elements are [geo, helio, bary, lsrk, lsrd, gal].

Uses

baryvel precess juldaytolmst

Version

$Id: chdoppler.pro,v 1.7 2009/12/01 17:33:37 bgarwood Exp $

Parameters
ra in, required	The source ra in decimal hours, equinox 2000
dec in, required	The source dec in decimal hours, equinox 2000
julday in, required	The julian day

Keywords
obspos in, optional double [2]	observatory position [East longitude, latitude] in degrees. Uses the GBT position if not specified.
light in, optional boolean	When set, returns the velocity as a fraction of c