Re: ski slope lighting

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

I have a folder of e-mails concerning that, the expert opinion of Nancy
Clanton has been published this way already, see

Re: ski slope lighting
        URL: http://amper.ped.muni.cz/jenik/letters/ski/msg00000.html

Another postings from the same day contain some info on Moon illumination
etc., but the folder concerns mostly my Czech correspondence regarding a
Czech project -- a totally horrible one.

My _compromise_ recommendation has been:

mean illuminance 0.5 lx (means 0.05 fc)
minimal illumin. 0.1 lx
maxima not over  2 lx

(important values are the minimal ones, these are sufficient as
moonlight experience confirms, in fact, the mean illuminance
needs not be over 0.2, with an excellent project)

And my strict demand has been luminance <=1cd/m2, what by a rather dark
snow means mean illuminance not over 4.9 lx. This way the well established
limit (common in the modern legislation of the regions of Italy) would be
obeyed. This is an absolute must (it has not be obeyed in the concerned
Czech case, they have used 40 lx probably for everyday purposes and
200 lx for competitions -- the only argument has been that these levels
are common in Alps).

There is no problem with vertical illumination, it is always sufficient,
thanks to the high albedo of the snow. To prove it computationally, the
illumination by the snow should be included, not just the direct
illumination by the luminaires (which may be the case for a poor project).

Far excessive ski slope illumination is one of the reasons of the
exponential rise of light pollution, we have to fight against its usual
practice. A project with moonlight levels means pollution as well, no
lighting is better than any lighting. But perhaps a good example like that
may help to reduce ten (or even hundred) times the existing slope
illuminations, if people recognise that moonlight-like zero-glare
illumination is sufficient, and that just such evening skiing is a real
pleasure. Of course, any artificial lighting should be switched off on clear
full moon nights!

happy skiing with natural lighting,

jenik