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Estimating Light Pollution Levels

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#1 Oscar56

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Posted 08 February 2013 - 08:46 AM

There is a light pollution map floating around that has been discussed on this forum. It gives a reasonable, but pretty coarse estimate of light pollution levels, especially if your location is near the boundary of 2 zones.

There must be a technique to estimate your actual light pollution level? Such as naked eye viewing of a specific constellation and determining what magnitude stars can be seen?

Grant

#2 CharlesW

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Posted 08 February 2013 - 10:53 AM

http://www.unihedron...jects/darksky/. It's an expensive toy but if you gotta know,,,

#3 Oscar56

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Posted 08 February 2013 - 11:01 AM

There's a toy for everything...

#4 mman22

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Posted 08 February 2013 - 11:08 AM

Grant,

Here is a link to a Dark Sky map. I like it because you can move and zoom for your area. This won't help give you a numerical value for the light pollution, but will help you find a good dark viewing site. http://www.jshine.ne...onomy/dark_sky/

#5 Oscar56

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Posted 08 February 2013 - 11:32 AM

Thanks mman22.

I have used this. According to this map my location is on the boundary between yellow and green.

The map gets pretty coarse when you get to about 1:500,000 scale, but is a good starting point to determine relative scale between different locations. Pretty handy if you are planning a trip somewhere and are interested in the light pollution level at your destination.

We might finally have some cloudless skies this weekend. I will see what magnitude stars I can see from my property, then compare that to the scale.

grant

#6 WaterMaster

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Posted 08 February 2013 - 12:00 PM

Hi Osccar, and welcome to Cloudy Nights.

Currently, the Globe at Night program is soliciting new data from the public ( GaN Family Activity Packet pdf ). This pdf has magnitude charts that are easy to use. They also have an interactive website you can use for real-time observations ( GaN webapp ).

The Globe at Night website, along with the International Dark Sky Association and our own Light Pollution Forum are great resources. :ubetcha:

#7 Oscar56

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Posted 08 February 2013 - 12:30 PM

Steve:

Well that's embarrassing. I totally missed the Light Pollution forum! Thanks for the links.

Grant

#8 WaterMaster

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Posted 08 February 2013 - 12:35 PM

No worries, we have have a lot of fora - I think I was a member for a few months before I scrolled all the way down to the bottom :lol:.

#9 Tony Flanders

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Posted 08 February 2013 - 01:31 PM

See my article Rate Your Skyglow.

#10 DHurst

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Posted 09 February 2013 - 01:21 PM

I have used this limiting magnitude estimation page:
http://obs.nineplanets.org/lm/rjm.html

#11 GeneT

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Posted 09 February 2013 - 05:55 PM

There are some good ideas in these posts. I am an old school :grin: guy. Before going out to view, I check over some sky charts of constellations that will be up. The stellar Mags are listed. I then see how dim a star(s) I can see. This method gets me pretty close.

#12 Oscar56

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Posted 09 February 2013 - 06:50 PM

Thanks everyone, some great resources mentioned here.

Now I need to wait for the winter cloud to dissipate.

#13 Oscar56

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Posted 10 February 2013 - 11:37 AM

Well the clouds did clear last night. I moved a lawn chair to the back deck put on my warm jacket and grabbed my iPad. I have SkySafari Plus loaded and turned on the night mode.

After 15 minutes, and with plenty of snow in the backyard, I was able to see to 3.5. I hope this will improve after the snow disappears, I stay out longer to acclimate my eyes, turn off more of the household lights. More trials will be required.

I have lots of hills and trees to work around, distant glow from Penticton to the SW, and local street lights to contend with but my backyard should be workable.

My binoculars should arrive this week. With those and SkySafari I should get a good sense of what I can see from the backyard and for what objects I will need to find a darker site. And perhaps later this year I will get a telescope.

#14 panhard

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Posted 10 February 2013 - 11:42 AM

Well Oscar it sounds like you are well on your way. :jump:

#15 Allan...

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Posted 10 February 2013 - 12:51 PM

Oscar, last night WAS an incredible night out. I cursed my neighbours's yard lights; they must've heard me because finally they turned them off. I got some great views of the Orion Nebula, Jupiters moons and also found two new galaxies (new to me, anyways)just to the North of the Big Dipper. Now, if we could just get Penticton (where I live...lol) to dim the lights more. Perhaps a spot out in Meadow or Garnet Valley would be great viewing for you. Im planning a trip to Darke Lake soon; its very black out there. Cheers, Allan :cool:

#16 Oscar56

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Posted 10 February 2013 - 01:09 PM

Allan:

What magnitude can you normally see naked eye in Penticton?

grant

#17 Allan...

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Posted 11 February 2013 - 12:16 AM

I couldn't answer that question, Grant. Not sure; too much of a newbie here...lol. Thought that tonight was going to be as good as last night but not so. The dew formed early and its getting hazy out; likely fog overnight. I PM'ed you; lets discuss the light pollution off line. thanks, Allan

#18 Starman1

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Posted 13 February 2013 - 01:23 AM

For rating your night sky, it's really hard to beat the Bortle Scale:
http://en.wikipedia...._Dark-Sky_Scale
Those of us familiar with a lot of truly dark sites would break down his best two scale levels into about 5 different levels, but it works nicely if describing a site to another person and you don't know the SQM readings for the site.

#19 Allan...

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Posted 15 February 2013 - 05:41 PM

Here's a neat little video on the difference between light polluted skies and dark skies. Link: Dark Skies






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