SED Data Model: Questions and Comments

[David Berry]

Sebastien asked me to forward this to the DM list.

David

---------- Forwarded message ----------
Date: Fri, 18 Feb 2005 20:53:34 +0100
From: Sebastien Derriere <derriere at newb6.u-strasbg.fr>
To: David Berry <dsb at ast.man.ac.uk>
Subject: Re: SED Data Model: Questions and Comments

David Berry wrote:
>
> AST can determine and evaluate mappings between any two equivalent
> units strings based on FITS-WCS paper I, with a range of tolerated
> variations (cm2->cm^2, micron->um, etc). This includes the log, ln, and
> exp functions which FITS-WCS paper I specified. But I cannot currently
> see how to do a dimensional analysis of say "log(Jy)/sr". Anyone got any
> ideas?

  In VizieR, the convention for writing units is to use brackets [] for
log of
quantities. So you'd write [Jy]/sr  So log can be expressed in the unit.

See documentation:
http://vizier.u-strasbg.fr/doc/catstd-3.2.htx
And tool:
http://vizier.u-strasbg.fr/cgi-bin/Unit

  But I have no idea as to the dimensional analysis of expressions
containing
a log??

Sebastien.

-- 
    _______
   /  ~   /, Sebastien Derriere   mailto:derriere at astro.u-strasbg.fr
  / ~~~~ //  Observatoire de Strasbourg    Phone +33 (0) 390 242 444
 /______//   11, rue de l'universite     Telefax +33 (0) 390 242 417
(______(/    F-67000 Strasbourg  France