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Thalestris24

The end of LP filters?

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With the increasing deployment of LED streetlights might it no longer be possible to use a lp filter of the kind that mostly works by cutting out the yellow sodium lines to reduce lp? Glasgow, where I live, is gradually replacing streetlights with LEDs. Unfortunately, I don't know the spectral details of said LEDs though I believe in general most are strong in the blue region and some types are warmer. I'd like to know the details of the ones being installed but can't find anything public (I suppose I should go for a walk after dark to see if I can find one). There are LEDs and there are LEDs - some better than others from an astro point of view. In any case they will in effect be broadband white light. I've looked at the (new?) Idas D2 but I'm not convinced - if anyone in a city with LED lighting has used one successfully I'd be interested to hear. I'm not sure how far they've got with the street light replacement (details are hard to find) but my judgement is that skyglow here has actually got worse over the last couple of years. It never did get properly dark where I am but whenever I try and do any imaging it's almost like twilight :( and I'm limited to 60s subs with a modded dslr and Idas lp filter. I bought a Baader 3.5nm Ha a few months ago - the skyglow even shows through that with long exposures :( (I know I really need a mono camera...). I so wish I could move! The relatively high humidity here doesn't help - it's like having an almost permanent layer of murk up above  If I had a car I could at least drive to somewhere a bit darker but I'm stuck. Still, I'll press on until the bitter end - and it probably will be bitter!

Louise

ps in the States

 

 

Edited by Thalestris24
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I used to work for a company as a physicist developing large area lighting panels, and the principle behind the majority of white LEDs is you use a blue LED diode and a yellow phosphor to achieve a white balance, so yes typically there is usually a strong narrow spectral peak in the blue, and a broader less strong peak in the yellow. An example spectra is shown below

image.png.f295eb08a9721a80016b2b85ea4d1b1f.png

For this purpose I have been considering supressing this blue peak in the LED spectrum by using a light yellow 495nm filter. It would be interesting to see if this helps. You could even combine this with a traditional LP filter to remove the Na emission lines from the spectrum. I believe this is the approach used by IDAS for the new D2

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The new IDAS D2 filter has been made with LED lights in mind. If you follow the link below, you'll see that they have manged to filter out pretty much all of the "blue" peak, and some of the phosphorescence - but not all. 

The move to LED's is worrying, but it would seem that the filter manufacturers still have a few methods of reducing it...  

https://www.firstlightoptics.com/light-pollution-reduction-imaging/idas-d2-light-pollution-suppression-filter.html

 

idas_d2_lps_transmission_graph.jpg

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Hello Louise. Any chance to "buddy-up" with somebody local with transport and similar interests?  Thanks for the interesting link.   :icon_biggrin:

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Just now, Peter Drew said:

Hello Louise. Any chance to "buddy-up" with somebody local with transport and similar interests?  Thanks for the interesting link.   :icon_biggrin:

Alas, I don't know anybody here plus one would have to be ready to go at a momen't's notice cos of the rapidly changing weather. Maybe I'll win the lottery...

Louise

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9 minutes ago, Ant said:

The new IDAS D2 filter has been made with LED lights in mind. If you follow the link below, you'll see that they have manged to filter out pretty much all of the "blue" peak, and some of the phosphorescence - but not all. 

The move to LED's is worrying, but it would seem that the filter manufacturers still have a few methods of reducing it...  

https://www.firstlightoptics.com/light-pollution-reduction-imaging/idas-d2-light-pollution-suppression-filter.html

 

idas_d2_lps_transmission_graph.jpg

Yeah, as I said, I'm not convinced, and don't know the actual details of LEDs being installed in Glasgow though I expect all will be revealed, eventually. If all streetlights become LED, then I guess there won't be any need for the specific sodium line suppression....

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21 minutes ago, Thalestris24 said:

 Maybe I'll win the lottery...

Louise

You'd have to enter it first and that would be a waste of money! :D

Ant's post is very encouraging. I didn't know about the anti-LED filters and had wondered about this.

What about the net amount of light being misdirected upwards? Is this going be reduced and so help the urban imager?

Olly

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36 minutes ago, ollypenrice said:

You'd have to enter it first and that would be a waste of money! :D

Ant's post is very encouraging. I didn't know about the anti-LED filters and had wondered about this.

What about the net amount of light being misdirected upwards? Is this going be reduced and so help the urban imager?

Olly

I've just been out and noticed some LED lamps near me. I might wander down and take some pics after sunset. That should show roughly how much is downward directed but it's hard to account for the whole city which is a mix of different lights and will be for some time to come...

Louise

 

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I have found here in Northants that the LED lights have improved the LP situation and most LP is coming from industrial units with misdirected lighting.

The best nights to get an idea are misty nights when you can see the light beams.

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Some while ago I went around my local streets at night with a handheld diffraction grating.  It clearly showed that the older (orange-ish) lights had line spectra while the white LEDs had a continuous spectrum with no obvious peaks.

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The LEDs near me are very well downward directed, so you can’t see dazzling lights extending all down the road. So I would hope they improve things over the dazzling HPS. Bluer light helps with Mesopic vision, but may reflect of the ground worse and won’t help you get to sleep if it seems in at night. Efficientcy and lifetime seem to be the main drivers, as long as they are well directed then we should hopefully see a reduction in LP. Many councils are running part night lighting, turning many lights off after midnight. Don’t give up.

PEter

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5 hours ago, Thalestris24 said:

 then I guess there won't be any need for the specific sodium line suppression....

An interesting thought, are there many low pressure sodiums still about ? Down here the only ones I have noticed are the high pressure sodiums which do not have the singular (almost) lines. But I could be wrong, I dont get out&about as much ! but the low pressure is very old tech now ?

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HPS are broad and centred around the orange sodium line, so you need to have filters that block a wider range of wavelengths. They installed a load near me which I guess I’ll be stuck with, though the latest load are LED.

PEter

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The local council have been installing LEDs throughout the borough. I think the LP is more dependent on the atmosphere than it was, even though they look to be well directed.

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Here are some (handheld and shaky) pics of some of my local lights. There is a new building just down the road from me (student accommodation) which has LED lights around it:

LED1.thumb.jpg.23d8cc53b7e6243a066e7e9c17ef6e1e.jpg

LED2.thumb.jpg.9064d9110af9de6de494bf74267d46ae.jpg

They are very bright! You can tell from the shadows on the building wall that most of the light is directed downwards. However, the high brightness turns the road into a secondary torch! :( . If you multiply that out... I believe ~60,000 streetlights are being replaced. 

White.thumb.jpg.0de8e1a1146289d47711defa39334cf6.jpg

Some of the other streetlights are yellow, others like this one are white but not LED and not so bright so the ground underneath isn't so brightly lit. Hard to tell how much of these lights goes upwards.

Flood.thumb.jpg.9cd3606511b2d9f1231f54db752fc38e.jpg

This what I see in my usual imaging direction (taken at 18:28). The floodlights really light up the whole area and don't go off until after 10pm. At least the reflective snow is thawing!

It's going to take some years to replace all the streetlights with LEDs and the AP situation will evolve. I'm not very optimistic.

Louise

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Ugh, that's horible Louise, and I thought I had horrid LP :(.

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OK so I no longer live there, and "y'all have decided to go away" but unless the UK wants to be the 'Wild West' of continental Europe, do what we do, simply have a policy to turn street lights OFF.

The only purpose that they serve IMHO is to help 'Crims' see where they are going, and use monetary resources granted by govt' to help in that endeavour!

I am in a pitch black location, torch required just to find the ML in the courtyard.

and we had a policy to turn the 'one and only'  street light around the Mairie off "when it goes dark"!*

Job done, it is now up to us.

 

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Unfortunately, UK cities are unlikely to ever switch the lights off - except during 'earth hour' - when it's always cloudy! Having said that, Glasgow does mention that LED lights would be more 'controllable' - a possible hint that the streetlight output might be modulated in some way under some unspecified circumstances.

Louise

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They have installed bright white LEDs in our village but on the old lamp posts which are angled up the way, a variety of different lamp heads some of which are so bright they hurt your eyes. Our local council did fit a shield on the one near our house as it lit up our bedroom even with blackout curtains.

While the rush to save energy/cash is in full swing by councils it looks as if they haven't really investigated retrofitting our street lighting properly.

The Americans  have recognised  a couple of years ago the damage that these bright white LED do.

http://theconversation.com/american-medical-association-warns-of-health-and-safety-problems-from-white-led-streetlights-61191

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43 minutes ago, Cyril said:

They have installed bright white LEDs in our village but on the old lamp posts which are angled up the way, a variety of different lamp heads some of which are so bright they hurt your eyes. Our local council did fit a shield on the one near our house as it lit up our bedroom even with blackout curtains.

While the rush to save energy/cash is in full swing by councils it looks as if they haven't really investigated retrofitting our street lighting properly.

The Americans  have recognised  a couple of years ago the damage that these bright white LED do.

http://theconversation.com/american-medical-association-warns-of-health-and-safety-problems-from-white-led-streetlights-61191

Yeah, there's lots of environmentally bad things to say about bright LEDs with a high colour temperature (see also my states link in my first post above). I'm tempted to contact Glasgow council and request that they consider choosing LEDs with lower brightness and lower colour temperature. I don't know who in particular to talk to - I'll have to do some research...

Louise

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This is a worrying story....

"The complaints were focused on the new fixtures being too bright, producing too much glare and light trespass, increasing skyglow and light pollution, and resulting in potential negative impact on human health and wildlife. "

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7 hours ago, Thalestris24 said:

This is a worrying story....

but very useful info.

Is some body in the UK learning lessons from this kind of experience to determine policy for the UK's move to LED?

Do the CPRE/IDA use this kind of info to try and influence local councils who are rolling out LED street lighting?

CS, Andy

 

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Louise, I do hope the situation turns out to be better than you had hoped. I can only echo PeterWs comments in that they have improved the situation around here. My back garden used to be between mag 18 and 18.5, now it is generally high 18s, at best around 19.2 ish if I remember correctly, certainly above 19. They dim later at night which does help too. They are generally much better shielded and directed, reducing upward

Dont give up, hopefully things will improve. Well worth exploring some of those filters too. I know it is inefficient but is it even possible to consider narrowband imaging with a DSLR??

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The enlightened Colchester Borough Council started turning off "unnecessary" streetlights between midnight and 04:00 to reduce carbon emissions and save money. Cue moans about an increased fear of crime (but no evidence of actual increase). Result, householders take their own action and we are suddenly surrounded by household floodlights. Then the Council cave in to pressure; switch a majority of street lights back on and we end up with double the light pollution as the new household PIR controlled  lights stay on or blink like a seaside pier illumination. So beware, campaigns to reduce light pollution can backfire.

Edited by noah4x4
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Yeah, it's the Monkey-Brain again, running around in little circles gibbering about leopards.

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