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General Astronomy >> Light Pollution

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DaveL
member


Reged: 09/30/09

Loc: Madison, WI, USA
Re: New Global Light Pollution Atlas new [Re: Tony Flanders]
      #6108232 - 09/29/13 09:23 PM

I definitely agree. I think you can only believe the trends in the light pollution maps if the trends are really big. Otherwise, the signal isn't big enough compared to the noise--so you can't be sure that the differences you are seeing are real light pollution or issues with satellite calibration, processing, plus the things Tony mentioned.

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Phillip Creed
Idiot Seeking Village
*****

Reged: 07/25/06

Loc: Canton, OH
Re: New Global Light Pollution Atlas new [Re: DaveL]
      #6108366 - 09/29/13 10:39 PM

I still find a bit odd that all of Ohio's major cities seemed to have "improved" (darkened) by about a half-zone. Could the lesser resolution of earlier data (1997, 2001) explain this?

Canton, OH, is in the bright red in 2006, but white in 2001. Columbus has a core of white, but mostly bright red, in 2006. In 2001, it was white all the way out to I-270. Toledo and Dayton had white zones in 2001 that are roughly equal in size the bright red zones in their downtown regions in the 2006 atlas.

Clear Skies,
Phil


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DaveL
member


Reged: 09/30/09

Loc: Madison, WI, USA
Re: New Global Light Pollution Atlas new [Re: Phillip Creed]
      #6109060 - 09/30/13 11:05 AM

I don't know why the bright areas have gotten darker according to the new data. The most obvious difference is that the 2006 data seems to pick up very weak light sources that are not present in the other data-sets. But this difference doesn't really have anything to do with the bright areas. I think all the satellites of this type have the same overpass time, so the issue doesn't involve that. Instead it must involve either satellite calibration or the processing of the raw satellite data. Since bright areas got darker and dark areas got brighter, I don't think calibration is the issue, instead I think it must be the data processing techniques.

I have just been comparing the 2006 data to some published CCD measurements over a wide range of sky conditions in Italy. The biggest errors between the light pollution atlas and the real data are in bright areas. It turns out that the bright areas are actually much brighter than suggested by the 2006 light pollution atlas, which suggests that maybe the 2001 data is closer to the truth in the bright cities. I'll try to post this soon, but first I want to check a few things.

-Dave

Edited by DaveL (09/30/13 11:09 AM)


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etatcloudy
journeyman


Reged: 03/26/12

Re: New Global Light Pollution Atlas new [Re: DaveL]
      #6449202 - 04/05/14 03:30 PM

Thanks so much for the update!!, would like to get the data into google earth. Easy to add the north america map as an overlay now just need to plug in the correct info on the location tab. Anyone know what's the location of the map?

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etatcloudy
journeyman


Reged: 03/26/12

Re: New Global Light Pollution Atlas new [Re: etatcloudy]
      #6449917 - 04/05/14 11:26 PM

So add image overlay using the NorthAmerica2006.png then for location use,
North 74°59'18.29"N
South 7° 0'5.54"N
East 51° 1'32.63"W
West 180° 0'0.00"W

Eyeballed but seems to work ok..


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TCW
Pooh-Bah


Reged: 11/05/13

Loc: The North 40
Re: New Global Light Pollution Atlas new [Re: etatcloudy]
      #6450127 - 04/06/14 01:35 AM

My area in the central Sierra Nevada seems to be much the same. Still dark blue.

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NorthWolf
Carpal Tunnel
*****

Reged: 02/23/09

Loc: Eastern Canada
Re: New Global Light Pollution Atlas new [Re: TCW]
      #6462119 - 04/12/14 01:12 PM

Amazing, thanks, I like the new blues, greens, yellows, etc

Edited by NorthWolf (04/12/14 01:14 PM)


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audioaficionado
scholastic sledgehammer


Reged: 05/24/12

Loc: Medford, Orygun, USA
Re: New Global Light Pollution Atlas new [Re: etatcloudy]
      #6468200 - 04/15/14 05:58 PM

Quote:

So add image overlay using the NorthAmerica2006.png then for location use,
North 74°59'18.29"N
South 7° 0'5.54"N
East 51° 1'32.63"W
West 180° 0'0.00"W

Eyeballed but seems to work ok..




Just did this and it seems good. Close enough to find my local dark areas IMHO.


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mantrain
scholastic sledgehammer
*****

Reged: 07/22/11

Loc: San Diego
Re: New Global Light Pollution Atlas new [Re: Tony Flanders]
      #6505071 - 05/03/14 11:25 PM

Really tremendous work!

I would like to ask if these are considered close to perfect?
The reason I ask is because where I live in E San Diego County
I have some excellent sub-urban to semi-rural sites from where I can see the milky-way and make out the stars of the U Minor. However those sites are shown in this map as red or orange which was a little surprising to me.


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Tony Flanders
Postmaster
*****

Reged: 05/18/06

Loc: Cambridge, MA, USA
Re: New Global Light Pollution Atlas new [Re: mantrain]
      #6505297 - 05/04/14 04:45 AM

Quote:

I have some excellent sub-urban to semi-rural sites from where I can see the milky-way and make out the stars of the U Minor. However those sites are shown in this map as red or orange which was a little surprising to me.




The summer Milky Way and all the stars of the Little Dipper should be very easy to see in the orange zone. I can see both fairly easily in all sites in the Boston area that are plotted in the red zone -- assuming, of course, that there are no nearby lights to blind me.


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Illinois
Carpal Tunnel


Reged: 12/18/06

Loc: near Dixon, Illinois USA
Re: New Global Light Pollution Atlas new [Re: Tony Flanders]
      #6507205 - 05/05/14 07:08 AM

Nice and I use it a lot to look around USA. Someday update something like 2020 then probably no blue zone in Florida! I see so much change around Orlando and Kissimmee! If you look at old map in 1955 and today....ouch!

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drollere
Pooh-Bah
*****

Reged: 02/02/10

Loc: sebastopol, california
Re: New Global Light Pollution Atlas new [Re: DaveL]
      #6649788 - 07/23/14 11:01 PM

Quote:

I've just calculated a new light pollution atlas from 2006 satellite data. You can find it here:

https://mywebspace.wisc.edu/dlorenz/web/astronomy/lp2006/

Enjoy!
Dave



the link quoted here is now (july, 2014) defunct.


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Octans
member


Reged: 08/13/09

Loc: Santa Barbara, CA, USA
Re: New Global Light Pollution Atlas new [Re: drollere]
      #6651158 - 07/24/14 07:13 PM

Here's a new link: http://djlorenz.github.io/astronomy/lp2006/

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drollere
Pooh-Bah
*****

Reged: 02/02/10

Loc: sebastopol, california
Re: New Global Light Pollution Atlas new [Re: Octans]
      #6651488 - 07/24/14 11:46 PM

that works.

i notice that attila danko's clear dark skies web site is now using the new maps.


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