[fitswcs] Paper III and radio/optical velocities

[Richard McMahon at IOA]

Hi Paddy,

	I wish I could do a smiley.

	I'll include the terminology in my next graduate course on
observational astronomy. In there with subject's like the differences
between B2000 and J2000 and epoch and equinox.

best regards richard

On Mon, 30 May 2005, Patrick Leahy wrote:

> Date: Mon, 30 May 2005 17:37:49 +0100 (BST)
> From: Patrick Leahy <jpl at jb.man.ac.uk>
> To: Richard McMahon at IOA <rgm at ast.cam.ac.uk>
> Cc: fitswcs at donar.cv.nrao.edu
> Subject: Re: [fitswcs] Paper III and radio/optical velocities
>
>
> On Mon, 30 May 2005, Richard McMahon at IOA wrote:
>
> <SNIP>
>
> > It would seem better to me to call them 'frequency' velocity, 'wavelength'
> > velocity and 'redshift' velocity if we are trying to describe data. The
> > optical/radio designations are not terms that real astronomers use.
> >
>
> Nonsense, many real astronomers use these terms all the time.
> Specifically, any radio astronomer who has had any contact with spectral
> line work will know of the two definitions and the trouble they cause.
> Obviously there are some optical astronomers (e.g. you) who havn't come
> across this before. You probably never measured a redshift small enough to
> approximate by a velocity without using a cosmological model, in which
> case the terms are indeed irrelevant for you.
>
>
> Paddy Leahy
>

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