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Hopefully my sky will get better in four short months.....

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#26 sg6

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Posted 15 April 2019 - 12:47 PM

The best way to consider it is: They are a different form of light pollution.

 

As the light is, or can be, directed downwards better then less gets to go sideways and upwards. The glow over a town is reduced, but it is still present, and it is white not yellow, just not as high above the town. There is reflection off the ground and walls etc.

 

When you are within the town then they are "worse". The intensity seems higher and you are in the pool of light - your night vision gets hammered. Bit like being in your living room with the light shining down.

 

Towns tend to go for the "WHITE" ones. One place around here has opted more for the cooler ones and they are oddly pleasant. Easy to see by for motorists and pedestrians, comfortable but clear. However places like that are rare (1?).

 

The bright white ones seem to make you look at them - bad idea. One at the end of my road, set so it manages to shine along the access path. Someone likely put a bit of thought into that. Would rather no light at all.

 

They can be shielded, but for cost they are not until someone complains - why waste time and money shielding something until required to do so. And then that is a seperately charged activity.

 

For whatever reason, here any way, they (most) get put on higher poles. Suppose the additional brightness means they can cover a greater area of ground. But they still have the same number of poles. They put the new higher poles where the old lower ones were - electric connections I suspect.

 

Waiting to find out what happens is in a way too late. Someone else will have decided for you and you get what they think is good. And that will be bright, intense, white light(s). So if you want input get along to whatever public consultations are available or planned.

 

Ask if the cooler options are available, can they be fitted if requested and ask if all can be shielded at the time of installation. The last would likely reduce problems and automatically fitting at installation could possibly work out less costly.

 

In a way they reduce light pollution - less light is going where it should not be going, but you will have more light. And "pollution" is it being in the wrong place.



#27 jgardner

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Posted 15 April 2019 - 08:12 PM

It's too bad for astronomers that white LEDs are indeed made from blue LEDs that light up a broadband-emitting phosphor.  If the LEDs were manufactured to emit discrete blue, green and red (and they could be), astronomical filtering would be possible.



#28 vsteblina

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Posted 18 April 2019 - 09:19 PM

It's too bad for astronomers that white LEDs are indeed made from blue LEDs that light up a broadband-emitting phosphor.  If the LEDs were manufactured to emit discrete blue, green and red (and they could be), astronomical filtering would be possible.

 

Can you comment more on your filtering of red, blue, and green light??

 

I kinda looked around and couldn’t find anything that hints that this works.



#29 barbarosa

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Posted 19 April 2019 - 05:30 PM

A red LED will have a peak engergy somewhere between 600 and 700nn  A green LED has a peak output at about 535nm. A blue LED peaks in the range of 450 to 470nm.

 

Bingo! All  you need is a filter that with pass bands that that exclud some or most of the undesireable ligtht near these wave lengths.  

 

There are possible problems. Street lighting with separate RGB LEDs might not have a uniform color as you approach and pass under the luminaire. These lamps if balanced for white would still emit considerable blue light,  Would an RGB lamp look better or worse or have more or less potential for glare or more important would it be acceptable to people in general and government officials in particular.


Edited by barbarosa, 19 April 2019 - 05:30 PM.


#30 vsteblina

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Posted 19 April 2019 - 06:54 PM

Here is a link.....https://commons.wiki...LED_spectra.png. This from 2005, but a more recent one I saw had much, much overlap.

 

However, I think that would be a great solution.....wonder why this hasn't been looked at for street lighting?? 

 

Anybody know??




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