[DSLF] Digest Number 1280

[DarkSky-list@yahoogroups...]

There is 1 message in this issue.

Topics in this digest:

      1. Re: MH vs. HPS
           From: "Fabio Falchi" <falchifa@tin...>


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Message: 1
   Date: Thu, 19 Feb 2004 11:29:11 +0100
   From: "Fabio Falchi" <falchifa@tin...>
Subject: Re: MH vs. HPS

Hi Guys,
I'd like to point out one important issue.
In order that the sky remain dark to the dark adapted eye, we need to keep
as low as possible the contribution of the light in the scotopic sensibility
range. If the sky is polluted only by 'outside scotopic band' light, we'll
detect it lighted only if it is so polluted that the photopic vision is
stimulated. So it is fundamental to keep the light in the scotopic band as
low as possible. It should be time to introduce some forbidden band, like
the ones in radioastronomy.The lumens of a LPS are far less pollutant for
the dark adapted eye than the same lumens emitted by a MH lamp.
Where it is mandatory to have a good color rendition it is not indispensable
to have an almost contiuum spectrum lamp (like HPS or MH), from blue to red.
We can have a three monochromatic lines lamp, one blue (less intense, due to
the more damage produced in the environment by blue light), one green (away
form the peak sensitivity of the scotopic eye and from Hbeta and OIII lines,
of course) and one red. This type of lamp pollutes only three very small
region of the spectrum and consequently it is easily filtered out.

Fabio Falchi

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FABIO FALCHI
Istituto di Scienza e Tecnologia dell'Inquinamento Luminoso - ISTIL
Light Pollution Science and Technology Institute
e-mail: falchi@lightpollution...
web: http://www.istil.it
     http://www.inquinamentoluminoso.it
     http://www.lightpollution.it/dmsp/
     http://www.pd.astro.it/cinzano/
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