[ATMoB-discuss] Re: [Nelpag] Dark Sky Presentation

[mmotta at massmed.org]

Thanks for the info and the corrections, I appreciate
that. Thanks for the PDF as well for those that want it
in that form.

Mario

On Thu, 30 Nov 2006 16:51:23 +0100 (CET), Jan Hollan
wrote:

> 
> >      Many have asked for a copy of the Light
> pollution power point I
> > developed for Gloucester. With Brewster LaMaccia's
> and Bernie Volz's
> > help, it is now available for all to use. Bernie was
> able to compress it
> > from my original 42 MB to a more manageable 8 MB
> download. (Due to all
> > the images I have imbedded). Feel free to copy and
> download, distribute
> > and use in any way that is useful.  I freely copied
> some slides from
> > others such as the IDA, from Bernie Kosicki from
> Acton Mass, and from
> > Susan Harder from Long Island. I have taken many
> examples of good and
> > bad lighting from Gloucester and surrounding towns
of
> the Cape Ann Area.
> > I suggest for a more powerful presentation, you also
> personalize it for
> > your local community. We are all in this together!
> > To download, the following is the link:
> >
> > http://atmob.org/~light/lightpollution.ppt
> > <http://atmob.org/%7Elight/lightpollution.ppt>
> >
> > If needed, copy that to your browser.
> > Mario Motta, MD
> 
> Mario,
> 
>  I've made a pdf from it for those who want to see it
> quickly or not adapt
> it at all. The ppt had still 14 MB, the pdf has just 5
> MB. I put it within
>  http://amper.ped.muni.cz/light/lectures/m_motta/
> 
> I made a small change within the pdf version of your
> excellent
> presentation (I went through it just quickly this
> noon), reducing the
> footcandles for the sunny beach to 12,000.00 fc from
> the original
> 30,000.00 fc. The reduced value should represent the
> possible maximum of
> natural illuminance. This is for a Sun in zenith and a
> location near the
> tropic of Capricorn at the beginning of January, when
> the Sun is closest
> to us. Sun shining through a clear hole in a white
> cloud could perhaps
> produce ten per cent more... but just for that moment.
> 
> Recycling light due to repeated bouncing off a snow
> plane and a cloud
> lower base, which amplifies light pollution at night
up
> to three times,
> does not work for sunlight, just one spot is
> illuminated through the hole
> in clouds, the rest of the landscape is in shadow. (I
> was wrong not
> realizing this in the last sentence of the second
> paragraph of my old
> posting
>    Linkname: Re: Moon Light
>         URL:
>
http://amper.ped.muni.cz/jenik/letters/public/msg00029.html ;
> meanwhile I gave lunar illuminance computation online,
>    Linkname: Illumination by the Moon
>         URL:
> http://amper.ped.muni.cz/jenik/astro/lun_illum.php ).
> 
> The whole common span of strongest natural
> illuminances, under which our
> vision works really well (and we can, e.g., read
> newspapers, even if not
> entirely comfortably at the very limits) is still one
> to one million:
> moonlight can achieve 0.02 fc just in winter, with
Moon
> high in the sky,
> July moonlight is always below 0.013 fc in northern
mid
> latitudes.
> 
> thanks,
>  jenik