No subject
Wed Feb 13 13:13:33 UTC 2008
now and the length of time the most recent snow cover has existed and the t=
emperature variations the cover has experienced (melting, refreezing meltin=
g...)=A0 Photometric measurements using simple instruments and conducted by=
interested persons could be used to generalize snow cover reflectivity.=A0=
The measurements would be made from several points in the illuminated area=
.=A0 One essential point would be directly beneath the source.=A0 Other poi=
nts would be along a straight line away from the first point.=A0 Remember, =
the intensity of the illumination falls of rapidly even from fully shielded=
sources.
=A0
Joe Mayer
=A0
--- On Sun, 12/20/09, Audrey Fischer <audrey at StarPals.org> wrote:
From: Audrey Fischer <audrey at StarPals.org>
Subject: [walnutpointobservatory] Re: [SQM] a "ground albedo influence" nig=
ht
To: "Jan Hollan" <jhollan at amper.ped.muni.cz>
Cc: ida at amper.ped.muni.cz, magnitude6 at yahoogroups.com, OutdoorLighting-Foru=
m at yahoogroups.com, sqm at unihedron.com, DarkSkyCommunities at yahoogroups.com, w=
alnutpointobservatory at yahoogroups.com, ida at darksky.org, "CAS E-Mail" <casre=
sponse at gmail.com>, "Volobog DNR" <DNR.Volobog at Illinois.gov>
Date: Sunday, December 20, 2009, 10:39 AM
Thanks Jan
This is very useful.
Also do you know whether there was even the slightest mention of light=A0=
=20
pollution issues during the entire Copenhagen Climate Change summit,=A0=A0=
=A0
interviews, or media?
:>)
Audrey
On Dec 20, 2009, at 10:16 AM, Jan Hollan wrote:
> Dear friends,
>
> just a reminder: a bright night with almost all landscape covered with
> cold white snow (here in Brno, just very concentrated salt water could
> thaw it recently) is an ideal opportunity to get the important number:
>
>=A0 =A0 =A0 =A0 =A0 =A0 what amount of sky luminance is due
>=A0 =A0 =A0 =A0 =A0 to the light disperesed from the ground
>
> This differs within towns and far from them, of course. But even=A0=20
> within
> towns, the amount of sky luminance due to direct emissions from
> luminaires is, fwith no snow, larger, unless the lighting is fully
> shielded.
>
> Comparison of snowless and snow-rich winter measurements (with the=A0=20
> same
> zenith extinction, if possible, or under a known one at least) is=A0=20
> our main
> tool in this respect. It can overweight any (wrong) models offered by
> polluters.
>
> Fabio and I have written about it several times already, but there=A0=20
> are not
> many data like that yet. We had a week with snow here in Brno=A0=20
> already, but
> this night is the first clear-sky one.
>
> So, don't miss the opportunity, if it will appear -- tonight or any=A0=20
> other
> night this winter.
>
> best,
>=A0 jenik
>
> PS. sorry for not responding to darksky issues at all, I'm=A0=20
> overwhelmed by
> working on the climate enlightment these months.
>
>
>
> _______________________________________________
> sqm mailing list
> sqm at unihedron.com
> http://unihedron.com/cgi-bin/mailman/listinfo/sqm
>
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<table cellspacing=3D"0" cellpadding=3D"0" border=3D"0" ><tr><td valign=3D"=
top" style=3D"font: inherit;"><DIV id=3Dyiv1764208742>
<DIV>Jan Hollan !!</DIV>
<DIV> </DIV>
<DIV>Hi, Jan. I'm Joe Mayer, the observatory director of the Chicago =
Astronomical Society and I've investigated this problem with an illuminatio=
n engineer from Portland, Oregon. I can't put my hands on the papers =
right now; nor can I remember the engineer's name. However, he is a f=
ormer board member of the IDA.</DIV>
<DIV> </DIV>
<DIV>His calculations and measurements produced the following res=
ults: Given a fully shielded illumination source such as a street lig=
ht, from a dry asphalt surface, 8% of the incident light is reflected =
into the atmosphere. From a dry concrete surface 25% of the incident =
light is reflected into the atmosphere. From a wet surface it's no pr=
oblem: It's raining.</DIV>
<DIV>From a snow covered surface the reflectivity is a function of the type=
of snow and the length of time the most recent snow cover has existed and =
the temperature variations the cover has experienced (melting, refreezing m=
elting...) Photometric measurements using simple instruments and cond=
ucted by interested persons could be used to generalize snow cover reflecti=
vity. The measurements would be made from several points in the illum=
inated area. One essential point would be directly beneath the source=
. Other points would be along a straight line away from the first poi=
nt. Remember, the intensity of the illumination falls of rapidly even=
from fully shielded sources.</DIV>
<DIV> </DIV>
<DIV>Joe Mayer</DIV>
<DIV> </DIV>
<DIV>--- On <B>Sun, 12/20/09, Audrey Fischer <I><audrey at StarPals.org>=
</I></B> wrote:<BR></DIV>
<BLOCKQUOTE style=3D"BORDER-LEFT: rgb(16,16,255) 2px solid; PADDING-LEFT: 5=
px; MARGIN-LEFT: 5px"><BR>From: Audrey Fischer <audrey at StarPals.org><=
BR>Subject: [walnutpointobservatory] Re: [SQM] a "ground albedo influence" =
night<BR>To: "Jan Hollan" <jhollan at amper.ped.muni.cz><BR>Cc: ida at ampe=
r.ped.muni.cz, magnitude6 at yahoogroups.com, OutdoorLighting-Forum at yahoogroup=
s.com, sqm at unihedron.com, DarkSkyCommunities at yahoogroups.com, walnutpointob=
servatory at yahoogroups.com, ida at darksky.org, "CAS E-Mail" <casresponse at gm=
ail.com>, "Volobog DNR" <DNR.Volobog at Illinois.gov><BR>Date: Sunday=
, December 20, 2009, 10:39 AM<BR><BR>
<DIV class=3DplainMail>Thanks Jan<BR>This is very useful.<BR><BR>Also do yo=
u know whether there was even the slightest mention of light <BR>poll=
ution issues during the entire Copenhagen Climate Change summit,  =
; <BR>interviews, or media?<BR>:>)<BR>Audrey<BR><BR>On Dec 20, 2009=
, at 10:16 AM, Jan Hollan wrote:<BR><BR>> Dear friends,<BR>><BR>> =
just a reminder: a bright night with almost all landscape covered with<BR>&=
gt; cold white snow (here in Brno, just very concentrated salt water could<=
BR>> thaw it recently) is an ideal opportunity to get the important numb=
er:<BR>><BR>> what amount of=
sky luminance is due<BR>> to the ligh=
t disperesed from the ground<BR>><BR>> This differs within towns and =
far from them, of course. But even <BR>> within<BR>> towns, the=
amount of sky luminance due to direct emissions from<BR>>
luminaires is, fwith no snow, larger, unless the lighting is fully<BR>>=
shielded.<BR>><BR>> Comparison of snowless and snow-rich winter meas=
urements (with the <BR>> same<BR>> zenith extinction, if possib=
le, or under a known one at least) is <BR>> our main<BR>> tool =
in this respect. It can overweight any (wrong) models offered by<BR>> po=
lluters.<BR>><BR>> Fabio and I have written about it several times al=
ready, but there <BR>> are not<BR>> many data like that yet. We=
had a week with snow here in Brno <BR>> already, but<BR>> this=
night is the first clear-sky one.<BR>><BR>> So, don't miss the oppor=
tunity, if it will appear -- tonight or any <BR>> other<BR>> ni=
ght this winter.<BR>><BR>> best,<BR>> jenik<BR>><BR>> =
PS. sorry for not responding to darksky issues at all, I'm <BR>> o=
verwhelmed by<BR>> working on the climate enlightment these
months.<BR>><BR>><BR>><BR>> __________________________________=
_____________<BR>> sqm mailing list<BR>> <A href=3D"http://us.mc814.m=
ail.yahoo.com/mc/compose?to=3Dsqm at unihedron.com" rel=3Dnofollow target=3D_b=
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mailman/listinfo/sqm" rel=3Dnofollow target=3D_blank>http://unihedron.com/c=
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QUOTE></DIV></td></tr></table>
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