Re: [SQM] Need some measurement guidelines

[Jan Hollan <jhollan@amper....muni.cz>]

> Using e.g. my star_pos programme (I could make it available
> online, if needed), the zenith extinction can be computed from such simple
> observation.
>
> jenik

It is online already, somehow.

Star names are to be written onto command line, in a bit awkward way:

``The point can be given through its HR number (in the Bright Star Catalogue)
 as
   HR#,
 or by its Greek/Flamsteed code (case sensitive!) preceded by `n' as
   nAlp_Cas nAlp1Sco n42_Eri ''

The URL for my online programmes is
             Computation of lighting-relevant values
        URL: http://amper.ped.muni.cz/jenik/astro/

Zenith extinction / 1 mmag in V, for two stars appearing equally bright,
 is the difference of their reported V (above atmosphere)
 divided by the difference of number of airmasses.

Of course, it would be nice to have two pairs of matching stars, in
different azimuths, to get a more reliable estimate and to identify a
possible involvement of transparent clouds affecting low-lying stars.

One of the stars can be a wandering star of course, whose ephemeris may be
computed e.g. via my programme planet, giving a proper parameter on the
command line of lun_illum.php
 (when clicking the ``[X] overriding all previous data'' option) -- e.g.
  c5 zm
 to get airmass for Jupiter, and
  c5 k2
 to get its V outside atmosphere.

Venus, Jupiter or Mars close to horizon are excellent objects to compare
with fixed stars near zenith.

I'd be very interested at your extinction estimates done this way, as a
mostly indoor astronomer, who has done quantitative visual observations
decades ago...

 wishing you both clear and overcast dry nights for measurements,

jenik

PS.
 The link to the source code and directory contains a bit old version
of star_pos (producing no final ``table'' in case of a single star).