[Astro]Re: Moon Light

[Jan Hollan]

I have corrected my programme regarding illumination by celestial bodies
(all but Moon gave nonsense in the draft, now the approx. solar
illumination is included, too). I took another lunar phase dependence,
from
   Linkname: Computing planetary positions, incl. brightness of Moon
        URL: http://hotel04.ausys.se/pausch/comp/ppcomp.html#15
 which is in accord with the Allen's old book. The differences from the
draft version are up to ten per cent (more light outside full moon now),
accuracy is probably no better than that. 

It seems that brightness of the Moon has been investigated thoroughly
just recently, to resolve the uncertainties and to get a reliable
calibration light source 
   Linkname: Robotic Lunar Observatory
        URL: http://wwwflag.wr.usgs.gov/USGSFlag/Space/LunarTel/index.html
 so better formulas may be available soon. 

My programme is able to compute illumination of any plain surface
now and has more suitable defaults, so 
  planet i0:0 c10 
 will compute the momentaneous direct clear-sky moonlight onto a southern
window. Default zenith extinction remains 20 cmag (ze20). Less messy
output for more than one day comes with MJD times instead, e.g.
  planet i c10 t23 d25 n6 mjd ne f43.681 l-114.363 ut-6
 for Ketchum horizontal direct lunar illumination starting from next
Thursday.

The corrected programme planet is again in 
 http://astro.sci.muni.cz/pub/hollan/programmes/

clear, just moonlit skies
Jenik

PS. 
 The author of the above page with the photometric lunar formula, Paul
Schlyter, has an interesting page on photometry,
   Linkname: Radiometry and photometry in astronomy
        URL: http://hotel04.ausys.se/pausch/comp/radfaq.html#10
 giving another natural (il)luminances as well.