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Best Light pollution map?

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#26 caveman_astronomer

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Posted 20 November 2017 - 02:38 AM

.......

 

Because of the proliferation of different maps using similar color schemes, it's getting almost meaningless to say "orange zone" without specifying which map you're using.

 

At least the color schemes are similar and usually follow the ROYGBIV mnemonic.  popcorn.gif



#27 bikerdib

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Posted 20 November 2017 - 09:12 AM

My thanks to the OP and to Jim.  I have not seen that map before but really like the interactive it uses.  My backyard at home is Bortle 4 like I already knew.  That's the good news.  The bad news is that there is a plant out near my weekend property / dark site that seems to be growing in brightness.  It is still a Bortle 3 site though, so far...



#28 Tony Flanders

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Posted 20 November 2017 - 09:54 AM

Forget all the LP maps for a moment and just look at the population densities of each county within about 200 miles of your prospective observing site.  Pick the least densely populated counties and then within those counties find the spots that are furthest from their respective cities, towns and major highways.


That works pretty well. The thing that the light-pollution maps include, which the above method does not, is a model for how light pollution spreads. For instance, the White Mountain National Forest in New Hampshire and Maine is a pretty big protected area with a few towns on inholdings inside it. Being resort towns, their nominal populations don't correlate very well with their degree of development. In addition, there are small cities to the north of the WMNF, modest-sized cities to the east and west, and cities ranging from big to huge to the south, but some distance away. The light-pollution maps give you a pretty good idea of how all those different sources balance out, and where within the WMNF might be best to look for the darkest sites.


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#29 jklein

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Posted 20 November 2017 - 10:09 AM

My thanks to the OP and to Jim.  I have not seen that map before but really like the interactive it uses.  My backyard at home is Bortle 4 like I already knew.  That's the good news.  The bad news is that there is a plant out near my weekend property / dark site that seems to be growing in brightness.  It is still a Bortle 3 site though, so far...

I find it interesting when there is a bright glow at some random spot in a reasonably dark zone. Feed the coordinates to Google Earth, and there is a big fat refinery/cement plant/etc sitting right there where it bothers only a few farmers/ranchers and those who seek darkness for legitimate reasons.


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#30 caveman_astronomer

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Posted 21 November 2017 - 06:07 AM

 

Forget all the LP maps for a moment and just look at the population densities of each county within about 200 miles of your prospective observing site.  Pick the least densely populated counties and then within those counties find the spots that are furthest from their respective cities, towns and major highways.


That works pretty well. The thing that the light-pollution maps include, which the above method does not, is a model for how light pollution spreads. For instance, the White Mountain National Forest in New Hampshire and Maine is a pretty big protected area with a few towns on inholdings inside it. Being resort towns, their nominal populations don't correlate very well with their degree of development. In addition, there are small cities to the north of the WMNF, modest-sized cities to the east and west, and cities ranging from big to huge to the south, but some distance away. The light-pollution maps give you a pretty good idea of how all those different sources balance out, and where within the WMNF might be best to look for the darkest sites.

 

One can look at the census data for recent decades and figure out which small-population counties aren't growing much. 


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#31 jklein

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Posted 21 November 2017 - 10:12 AM

 

 

Forget all the LP maps for a moment and just look at the population densities of each county within about 200 miles of your prospective observing site.  Pick the least densely populated counties and then within those counties find the spots that are furthest from their respective cities, towns and major highways.


That works pretty well. The thing that the light-pollution maps include, which the above method does not, is a model for how light pollution spreads. For instance, the White Mountain National Forest in New Hampshire and Maine is a pretty big protected area with a few towns on inholdings inside it. Being resort towns, their nominal populations don't correlate very well with their degree of development. In addition, there are small cities to the north of the WMNF, modest-sized cities to the east and west, and cities ranging from big to huge to the south, but some distance away. The light-pollution maps give you a pretty good idea of how all those different sources balance out, and where within the WMNF might be best to look for the darkest sites.

 

One can look at the census data for recent decades and figure out which small-population counties aren't growing much. 

 

I'm looking for dark sky land within an hour or two drive from my home. Maybe 10 acres - if it is cheap enough, that will mean it is less likely that some developer has an eye on it. Some of the places are hunting leases, etc. Don't know if that would continue if I owned it, but it might. At most I would want to put out a few pads for scopes so we could have impromptu star parties. It was a real disappointment to have to schedule a dark sky site two months in advance (prepay!) only to have the weather turn sour at almost the last minute. I will see how the two or three club dark sites work out for spur of the moment trips before doing that though. And retirement means there will be more middle-of-the-week opportunities.



#32 George N

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Posted 28 November 2017 - 10:44 AM

 

My thanks to the OP and to Jim.......

I find it interesting when there is a bright glow at some random spot in a reasonably dark zone. Feed the coordinates to Google Earth, and there is a big fat refinery/cement plant/etc sitting right there where it bothers only a few farmers/ranchers and those who seek darkness for legitimate reasons.

 

My recent experience with this (NY/PA border area - mostly PA's Endless Mountains):

 

    It was not a "random bright spot in a dark zone" it was a patch of mostly low-population forest that suddenly became the brightest source of nighttime light within a 100 miles - much brighter than a small city with 80,000 people in the same area!

 

    What was it? Gas frack'ing! Long lines of trucks on rural roads, huge lit parking and equipment storage areas, drill pads lit brighter than daytime, spotlights blasting up at drill towers, and of course towering columns of burn-off gas as tall as a 10 story building providing a pretty flickering light that can be seen for miles (not to mention sounding like a 747 stuck over your head). At least now, with drilling temporarily suspended (gas prices down) things are a lot better, but there are still plenty of new lights - including those going in at the pumping stations and pipeline nodes.



#33 Spata

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Posted 18 December 2017 - 02:31 PM

 

A lot of folks use this one - https://www.lightpollutionmap.info

Click on the red Atlas in the menu in the upper right. Then when you click on various spots, it will give Bortle rating as well as the one I don't understand as much.

 

Unfortunately, this map system is quite inaccurate. I find that for New York and New England locations it typically provides values significantly too low on the Bortle scale for even modestly populated areas, while at the same time rating darker semi-rural locations as far too bright.

 

BrooksObs

 

I also believe that site to be fairly inaccurate. It gives my location a Bortle 8-9 but using this as reference: https://en.wikipedia...ki/Bortle_scale I believe my location is a 6-7 on most nights. When my schedule and the weather cooperate I can find and see the glow of Orion with little to no effort, Pleiades is obvious, Andromeda is a grey/white smudge and the Beehive Cluster, while harder to find, can be seen.



#34 hantunes

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Posted 07 May 2019 - 09:38 AM

A lot of folks use this one - https://www.lightpollutionmap.info

Click on the red Atlas in the menu in the upper right. Then when you click on various spots, it will give Bortle rating as well as the one I don't understand as much.

Hi there,

 

I wonder if it anyone could tell me if this map is updated, I mean:

 

The area where I leave (Leiria, Portugal - western point of Europe), has suffered a major fire a couple of years ago by the seashore. Therefore, there are some points on the map marked in green (Coordinates 39° 49′ 28″ N 8° 59′ 19″ W) where I could try to take some photos. Though this is not the ideal place to look at the sky, the way I see things is that with this fire, the shore is now more affected with the light pollution from the nearby cities.

 

Considering this, are you able to tell me if this website already reflects the nowadays reality or, instead, is only calculating the proximity to artificial lightning the same way it was before the fire?

 

Thank you for your help...



#35 Tony Flanders

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Posted 07 May 2019 - 06:45 PM

Hi there,

 

I wonder if it anyone could tell me if this map is updated, I mean:

 

The area where I leave (Leiria, Portugal - western point of Europe), has suffered a major fire a couple of years ago by the seashore. Therefore, there are some points on the map marked in green (Coordinates 39° 49′ 28″ N 8° 59′ 19″ W) where I could try to take some photos. Though this is not the ideal place to look at the sky, the way I see things is that with this fire, the shore is now more affected with the light pollution from the nearby cities.

 

Considering this, are you able to tell me if this website already reflects the nowadays reality or, instead, is only calculating the proximity to artificial lightning the same way it was before the fire?

 

Thank you for your help...

These maps never had enough sophistication to take things like tree cover into account. In fact most of them don't even take topography into account, and mountains are known to play a major role in blocking artificial light pollution.

 

In other words, all the maps are pretty vague approximations, with no guarantees at all about how well they match reality. Good enough to get a decent guess about how two different locations compare to each other, but nowhere near good enough for scientific studies of skyglow. For that, you need actual measurements from the ground, not from a satellite.


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#36 hantunes

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Posted 16 May 2019 - 08:49 AM

These maps never had enough sophistication to take things like tree cover into account. In fact most of them don't even take topography into account, and mountains are known to play a major role in blocking artificial light pollution.

 

In other words, all the maps are pretty vague approximations, with no guarantees at all about how well they match reality. Good enough to get a decent guess about how two different locations compare to each other, but nowhere near good enough for scientific studies of skyglow. For that, you need actual measurements from the ground, not from a satellite.

Thanks a lot.

 

I didn't have a clue about how they worked.



#37 Sky_LO

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Posted 05 October 2019 - 06:38 PM

For me, in my area, there are smaller towns (50,000 or less population) with space between towns. 

and larger towns (250,000 - 500,000) about an hour away.   

 

When I visit observing sites and try them they seem to line up really well with my expectations

from the lightpollutionmap.info map.  

 

I have seen where many folks really dislike the LPmap.info site.  

 

It may be more accurate where I live because of the spacing between towns? 

Anyway, I like the site a lot and it works well - for me - and I find it quite useful.    

 

-Lauren 


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#38 jdown

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Posted 15 October 2019 - 03:30 PM

Seems like many members like this map; it's pretty accurate for my location; however I'm not in a populated area.

I also use lightpollutionmap.info.  Like another on this thread, I don't understand its radiance values, only that the smaller the number, the darker the site.  

 

Just out of curiosity, for those who use this map, what is the minimum difference in radiance values that a person with normal eyesight would actually notice?  Or does it suffice to say that any dark site within an area whose Bortle scale is, say, 2, will appear the same as any other spot in an area whose Bortle scale is 2 ?? 



#39 Sky_LO

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Posted 16 October 2019 - 12:03 AM

Jdown..nope!  .it would be very nice if it were that easy! 

In actual practice there is a large range within each bortle zone! 



#40 sg6

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Posted 17 November 2019 - 10:48 AM

Will say that lightpollutionmap.info needs an update, just checked where I am and places I visit, everything is either B5 or B4. Nothing else seems to exist.

 

Checked out where they hold a twice yearly star party and still B4. Will say that the middle of the North Sea some 30 miles from everything and no oil platforms comes out as B3.

 

Another one I looked at said they like the Bortle scale of 9 bands, then the scale they have uses 15 different colors. So not actually matching Bortle either for all they like it.

 

Final one and after which I gave up looking has a scale of:: (NanoWatts/cm2/sr)  shocked.gif shocked.gif shocked.gif

So a very obvious scale that everyone intuitively understands - I think not.

 

Many here seem based on population, so if 500 people live whereever then the place is colored Red or Green or whatever 500 people apparently implies.

 

One Bortle explanation says M31 is naked eye (just) at B6. Scales seem a bit random.


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#41 Tony Flanders

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Posted 17 November 2019 - 06:53 PM

Will say that lightpollutionmap.info needs an update, just checked where I am and places I visit, everything is either B5 or B4. Nothing else seems to exist.


My guess is that to some extent, that's a genuine fact about where you live.
 

One Bortle explanation says M31 is naked eye (just) at B6. Scales seem a bit random.

Here is John Bortle's description of Class 6:

No trace of the zodiacal light can be seen, even on the best nights. Any indications of the Milky Way are apparent only toward the zenith. The sky within 35° of the horizon glows grayish white. Clouds anywhere in the sky appear fairly bright. You have no trouble seeing eyepieces and telescope accessories on an observing table. M33 is impossible to see without binoculars, and M31 is only modestly apparent to the unaided eye. The naked-eye limit is about 5.5, and a 32-cm telescope used at moderate powers will show stars at magnitude 14.0 to 14.5.

The entire article is here.
 
How well this correlates with any map or measuring device is unclear. Light-pollution maps should definitely be taken with many grains of salt.
 
It's worth pointing out that hardly anybody except Bortle thinks that all the different criteria that he lists for his classes correlate well with each other. For instance, I rate my country home as Class 4 by most criteria, but 5 or even 6 by others.


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#42 mr.otswons

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Posted 20 November 2019 - 01:19 PM

Do I understand correctly that the light-green area covering the entire polar region north of Island is due to VIIRS registering light radiating from the polar ice and snow? Surely it isn't because of data collected during polar day and therefore sunlit 24/7, then it would be more in a straight line and not having a dip around Greenland?

If it is ice and snow, does it affect visual observing in any significant way compared to a site closer to equator, if both sites are equally distanced from any artificial light sources and are equal in every other way?

 

It seems that most of the large modern observatories are build down south, and not in polar regions. I have read some articles about Polar astronomy, but there are not many to find, except of the obvious Aurora Borealis research.

Why is Polar regions not popular for professional or amateur astronomy? Myself is living in Oslo, Norway, but frequently I am traveling to Northern Norway and neighbouring Russian city of Murmansk. Weather is so-so: many clouds, winter-storms, cold. Apart from that we have 9 months of darkness, and that should count for something.

 

I see that my post started with one question, but indulged into an area of discussion in the second part, perhaps suited for another forum or topic. Disregard the second question then, if that is so.

 

PS: I am a visual observing beginner with many questions, (probably not uncommon). Still working on making an observation routine and find an area to focus on. Leaning towards double stars and planetary. But first learning how to orientate myself in the night sky, using equatorial mount and charts, and learning the technical and theoretical aspects of optics and mechanics of a telescope setup by building a refractor with GEM on a steel pier.

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#43 krneki

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Posted 30 November 2019 - 08:27 AM

It's from Aurora Borealis. As can be seen it's even over the sea. During the polar day VIIRS data isn't being collected by the satellite. You can see how the terminator moves if you switch between monthly datasets (upper right icon) in the light trends application: https://lighttrends....lutionmap.info/



#44 mr.otswons

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Posted 01 December 2019 - 02:02 PM

Thanks for the input. But does it mean that VIIRS does not collect data/register light coming of the ice and snow?

Here is a picture made by the Suomi satellite of actual northern lights... 

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#45 krneki

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Posted 02 December 2019 - 04:58 PM

It does, but something has to illuminate the snow. In remote areas this can only be stars, auroras, air glow or zodiacal light (gegenschein).


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#46 mr.otswons

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Posted 03 December 2019 - 04:41 AM

It does, but something has to illuminate the snow. In remote areas this can only be stars, auroras, air glow or zodiacal light (gegenschein).

It's interesting to think how sensitive VIIRS is, since northern lights are not very bright to illuminate the snow and ice, at least for the human eye.




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