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What is Radiance Information

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#1 WALee

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Posted 26 July 2017 - 02:18 AM

Looking at the Light pollution map of my home location I get a Radiance Information value of 17.36. Tonight I drove several miles north and found a pretty dark site. The Radiance Information value for that spot was 0.78. Can anyone tell me what this means? 

 

Thanks

Tony



#2 caveman_astronomer

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Posted 26 July 2017 - 06:25 PM

You should see some very faint red lines marking off squares about 1/4 mile on a side.  Anywhere within a particular square you will see the same reading.  I suspect this number represents the amount of light being emitted from within the square as a whole.  The square to the north of me has more trees and a lower number.  The square to the east of me has more houses, fewer trees and a higher number. A square 1/2 mile to the west has some commercial areas and an even higher number.

 

For astronomy, we want fewer trees and fewer buildings.  Except our own, of course.  Those are OK.lol.gif



#3 WALee

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Posted 26 July 2017 - 07:27 PM

Thank caveman_astronomer, I think you are correct. Did some research today and it seems it is a measurement of emitted and/or reflected light.

 

I was using this map and it doesn't have the little red squares. 

 

https://www.lightpol...yers=B0TFFFFFFF

 

I would be interest to know which map you are referring to.

 

Thanks so much for your input

Tony



#4 caveman_astronomer

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Posted 27 July 2017 - 08:36 AM

Thank caveman_astronomer, I think you are correct. Did some research today and it seems it is a measurement of emitted and/or reflected light.

 

I was using this map and it doesn't have the little red squares. 

 

https://www.lightpol...yers=B0TFFFFFFF

 

I would be interest to know which map you are referring to.

 

Thanks so much for your input

Tony

You have to zoom in far enough for the squares (rectangles) to appear.  Try 500m on the scale in the lower left of the screen and then click on the Radiance Point tool.


Edited by caveman_astronomer, 27 July 2017 - 08:37 AM.

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#5 earlyriser

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Posted 27 July 2017 - 12:27 PM

You should see some very faint red lines marking off squares about 1/4 mile on a side.  Anywhere within a particular square you will see the same reading.  I suspect this number represents the amount of light being emitted from within the square as a whole.  The square to the north of me has more trees and a lower number.  The square to the east of me has more houses, fewer trees and a higher number. A square 1/2 mile to the west has some commercial areas and an even higher number.

 

For astronomy, we want fewer trees and fewer buildings.  Except our own, of course.  Those are OK.lol.gif

The mature trees lining the streets in my area appear to shield the sky from a lot of the horizontally emitted light from streetlights. So they're not all bad.




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