LED Street Lights Are Bad For Astronomy

[laser_jock99]

http://spie.org/x115768.xml?highlight=x2408&ArticleID=x115768

"The steady global conversion to white LED lighting, especially for streets, is the biggest problem we have confronted in the 27-year existence of the Dark Sky Association," says John Barentine, project manager for the IDA.

Pretty much what some of us have been saying for a few years- broadband & back scatter.

[Rockenrock]

I was wondering about this issue a few days ago. There is a huge conversion to LED going on, I think because of long life (less maintenance).

Is the LED problem because the light is broad range of frequencies, and cannot be filtered out without degrading the star photons?

Is back scatter different for LED?

Clear and dark skies!

     Roger

[Psychobilly]

The light is a lot more intense and while its directed downwards theres a lot more of it reflected back into the sky... If the reflectivity of the ground increases after  rain , frost or snow it gets even worse...

No possibilty to filter it out my expensive LP filters are now worthless pieces of glass...

The change is pretty much the nail in the coffin for me unless they introduce dimming or even better part time lighting... At the moment all the ones for miles around seem to be on at full brightness all night long...

Peter...

[JamesF]

Whilst I agree with the general tone of the article and that direct light from LEDs is very difficult to filter, I'm really not convinced that well-installed LED lighting generates greater sky-glow than traditional sodium lighting.  Many of the pieces I've read claiming it does don't seem to be doing so on the basis of credible scientific measurement, but rather by an "appeal to common sense" which is as often as not completely wrong.

I'd very much like to see some references to proper research rather than people just claiming it's obvious.  Even that photo of Milan is completely misleading.  The matching photo taken prior to the LED conversion shows the city centre to be noticeably brighter than the suburbs too, and there are areas where the original lighting is clearly brighter than its replacement.  In fact, whilst the streets may look brighter after LED lighting was fitted, the darker areas between look like they might be better defined too, so I'd say it's impossible to draw any reliable conclusions from it, even more so given that we don't even know that they were taking in comparable conditions.  Perhaps publishing both images together would have impacted on the plausibility of the article however

I have no idea what conclusion such research might draw.  I can see plausible reasons that either type of lighting might be worse for skyglow than the other.  Perhaps given the nature of the light they produce they might even each be worse in different atmospheric conditions.

James

[ChrisLX200]

So why could they not have chosen an LED that outputs a single wavelength of light that is easy to filter out?

ChrisH

[Psychobilly]

  Perhaps given the nature of the light they produce they might even each be worse in different atmospheric conditions.

James

Any moisture in the air and it's horrendous...

Do you have them around you at the moment? Unfortunately I do...  Two of them within a few metres of my obs...

What used to be one of my darkest directions pre-LED and a cinch to filter out  is now one of the worst with the glow from the next valley over evident way up into the sky... The only thing that's improved is the view straight up!!

I make no apology for re-posting this image...

There's a lot of info with links to scientific papers on the Wikipedia entry  for LED streetlights...

https://en.wikipedia.org/wiki/LED_street_light

http://www.dynamics.org/~altenber/PROJECTS/MAUI/STARRY_NIGHTS/ARTICLES/Falchi+Cinzano++Haim_limiting.2011.pdf

http://www.sciencedirect.com/science/article/pii/S0022407313004792

http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0067798

Peter...

[Tim]

Coventry used to be bad, now it is impossible, and they arent all done yet

[Alien 13]

I have found that the changes to LEDs for me living near to a city center are huge I can easily see the milky way now.

Alan

[dph1nm]

Hmm - our estate has had LEDs installed and I have to say it has improved things (so much so that non-astronomers have been complaining it is now too dark to walk!). They are far better shielded than the old sodium lights (wouldn't be difficult as they weren't shielded at all). The worst problem I now have is the high pressure sodium lights they have recently installed on the main road, which are numerous. very tall and unshielded.

NIgelM

[Paul M]

The lighting down my street is just being "upgraded" to LED. They aren't powered up yet but they appear to be very well shielded so perhaps much less direct glare than the old sodium lighting?

I'm doomed anyway, My back yard is bright enough to read by on most "dark nights" and  we currently have Blackpool's Illuminations glaring directly to my south.

Of greater concern is the creeping glare at my "dark sky" site in Rural Cumbria. Over the last 12 years I've noticed it isn't as dark as it used to be. I do wonder if it's due to a change in the type of lighting in Penrith 5 miles to the north.

My employer recently spent a fortune on changing the huge amount of fluorescent and sodium lighting to LED on the industrial site where I work. The glare from the LED floodlights is dreadful and the workspace lighting has a "flat" quality to it. Not nice for working with. Apparently they will pay for themselves by way of greatly reduced electricity bills. Having seen my employers electricity bill I fully understand why they have done it but I'm not sure they factored in maintenance. They are always failing or flashing.

Luckily, on a night shift, I have control over the lighting and can turn it off as required

Anyway,at my last eye test I asked the optometrist if there was any sign of cataracts in my eyes. They are perfectly clear (other than the dreaded floaters ) so my discomfort must be down to the new lighting.

I think us astronomers (and anyone who is aware of and exercises their visual acuity) are very sensitive to optical effects that many others just don't notice .

[davedownsouth]

In Spring of this year they installed LED light in our street, which are left on all night, and I would have to say that the views from my backgarden have improved.  If the Moon is less than half, I can see the Milkyway, and on Moonless nigths it is very easy to spot.

[JamesF]

We can't afford proper streetlights around here.  We have to use our own hand-held portable ones.

There are some LED lights in the local town and I have been quite impressed with how clear the difference is between the lit and unlit areas, but there aren't really enough to make a judgement on.

James

[John]

In Spring of this year they installed LED light in our street, which are left on all night, and I would have to say that the views from my backgarden have improved.  If the Moon is less than half, I can see the Milkyway, and on Moonless nigths it is very easy to spot.

I'm in just the same situation and have the same result.

Clearly the impact that LED lighting has varies depending on a whole lot of local factors including dew / frost fall.

[laudropb]

Have to agree. It seems there are good and bad experiences. The change over to LED here has definitely improved things here. Skies are definitely darker. The lamps are very well shielded and directed.

[Alien 13]

The one bonus of LED lighting is that at some point in the future their are options to dim them.

Alan

[JamesF]

Perhaps some of the perceived difference on the ground in relatively close proximity is down to the design of lamp?  Presumably some designs must be better at controlling the direction of the light than others.

James

[NigeB]

Hi All,

The SPIE article is certainly a bit depressing, but I think there is cause for some optimism - if not universally so...

First, the peer-reviewed papers which Peter cites certainly support the view that the spectral power distribution of broadband LED's can lead to increased scatter and skyglow amongst other problems. The blue-rich spectral distribution, and the overall intensity, of the LED sources are key contributors to this.

But (based on an admittedly quick reading), it appears that the analysis is confined mainly to the properties and effects of the emission source, and not the housing it is in. That is made clear in the writing, and is entirely appropriate in the context of these research papers, which aim to consider the effects of illumination sources evaluated against a common baseline (so for example, Luginbuhl et al assume a fixed fraction of upwardly directed energy). This is an important input for people like planners and lighting designers, but it's only part of the picture that concerns us.

Falchi et al. adopt the same methodical approach, but they acknowledge the critical role that the fitting design has on the effects of the source - the importance of effective cutoff designs to minimise light spread, etc.

The posts by NigelM, Alan and Tim suggest very different experiences of LED lighting, and I think that this is likely due to the design of the housing. I live near Oakham, in a village where LED streetlights have recently been installed, in very effective full cutoff housings. The light underneath these is unquestionably more intense than the old fittings. But my skies are noticeably improved because of the full cutoff design, which the older lights didn't have. (That they turn off the new lights after about 1 AM, is a bonus - but even before that hour, it's improved). I suspect that the fittings used in Leicester, about 20 miles away from me, are of a similar design, hence Alan's experience.

This means that the old arguments we had to use to combat light pollution in the pre-LED days - like properly positioned lights which are effectively directed and have full cutoff housings, are even more relevant now. But previously, we were arguing for investment to upgrade or modify fittings which (as far as the local authority was concerned) needed little or no attention - they were being asked to replace, at expense, a perfectly serviceable light. Sure, if we had managed to get full cutoff fittings and sensibly timed on/off periods implemented with the old low pressure sodium lights, things would have been much better. But was that ever a realistic prospect?

The advantage now, is that if councils want to change to LEDs (which they do, for the economic benefits), they have to change the fitting design as well. So the change to LED could be seen as a window of opportunity to combat light pollution: it's no longer the astronomers who are the fundamental cause of the expenditure, the change is being made anyway, and we can try and influence the choice of design so that everyone benefits.

Clearly this isn't working for everyone - the light on the left side of Peter's image looks like a poorly designed one, and I'm not doubting the reports from Coventry and elsewhere (it would be interesting to see some photos of the Coventry and Leicester fittings). But I think the experience in Leicester and Rutland, indicates that the move to LEDs isn't necessarily a step backwards, if the change in emission source is accompanied by selection of the proper fitting.

Nigel

[FenlandPaul]

So why could they not have chosen an LED that outputs a single wavelength of light that is easy to filter out?

ChrisH

I tried to explain this in post 29 of http://stargazerslounge.com/topic/244373-what-colour-should-streetlamps-be/page-2

The trend in streetlights has been towards better colour rendition, which inevitably means more wavelengths involved than the fine emission lines of low pressure sodium. So whilst red everywhere would be great for us astronomers, the general public would be less impressed!

Paul

[JamesF]

I think also that when driving humans ideally need a reasonable spread across the spectrum to be able to properly interpret what's going on around them.

I hate driving under sodium lighting before it reaches full brightness and even when it does reach full brightness I can never quite get rid of the misgiving that I can't really see things quite as well as I'd desire in order to feel like I was properly aware of my surroundings.  It may be the way that dissimilar colours that I'd normally notice in an instant can blend into one under sodium lighting giving the feeling I'm likely to miss something, especially in peripheral vision.

James

[FenlandPaul]

I think there are some interesting points that the article raises, and even more interesting are the real life experiences of people on this forum.

As some of you know, I work in this industry. I help run an industrial LED lighting business. We're not big into streetlights - mainly selling into big industrial facilities - but it does form a small part of what we do for certain private roadways. It's up to you whether you think I'm conflicted in my comments below!!

First off is the extraordinary quote from the IDA: "This now puts us in the awkward position of opposing a brand-new lighting technology that promises substantially lower electricity use and cost savings.". Now some of the fixtures that we manufacture have received the "Fixture Seal of Approval" from the IDA. I pay $250 for each fixture and an annual renewal fee of about 10% of that. The IDA state in their blurb about the FSA that colour temperature of LEDs is a concern for them (see here: http://darksky.org/fsa/)but they're still prepared to take cash from me and give my lamps an approval, despite also saying they oppose LED lighting in the quote above. I'm sorry, but that strikes me as inconsistent at best. Interestingly, some manufacturers don't recognise the IDA approach as having a sound basis; one example (a very credible, experienced lighting organisation) is these guys: http://www.holophane.co.uk/darksky.html

The studies cited in UK and Chicago about no correlation between increased lighting and reduced crime and accidents is a little out of context. The studies appear to be talking about intensity of lighting rather than colour / temperature; my understanding is that colour rendition is absolutely a contributor to reduced accidents, because drivers are less tired and you don't get changes in visibility of pedestrians depending on the colour clothes they're wearing.

The article is full of oblique references to many good quality studies about excessive / poorly directed lighting and then infers the studies are mainly or mostly about LED lighting. That's just misleading. And lazy.

The comments on poor directionality are interesting. Unfortunately that's always going to be down to the installer and the lighting designer. LEDs are about as directional as it's possible for a large areas light source to be, so if anyone suffers from poorly directed light it's because either the wrong fixture has been installed or the installer hasn't done their job properly. My advice to anyone who is suffering from poorly directed LED lighting is to challenge the local authority on the execution of their lighting project. There will definitely be a fix.

"Rather, we expect cities to light more because for the same dollar cost they can operate significantly more fixtures". I'm not sure that will be the case, although naturally there will be exceptions. Without fail the customers I encounter want to reduce their energy bill as much as possible, employing daylight / twilighht sensors, occupancy sensors etc to help with this, and to improve the quality of lighting for safety and productivity reasons. Lighting more space just isn't something I see happening on the ground. I hope it stays that way!!

I don't mean to sledge the article. But there is an awful lot of hype and misinformation about this new technology. It represents a huge opportunity for us to reduce our energy consumption, which isn't something we can ignore. As an amateur astronomer I'm hugely concerned about night sky quality; it's my firm belief and my experience, shared with many on this forum, that LED lighting can be hugely beneficial to visual observation if used and directed properly. It's more of a challenge - undeniably - to imagers but I wonder what technology can be employed to help filter out some of the effects.

I look forward to hearing others' views.

[FenlandPaul]

My employer recently spent a fortune on changing the huge amount of fluorescent and sodium lighting to LED on the industrial site where I work. The glare from the LED floodlights is dreadful and the workspace lighting has a "flat" quality to it. Not nice for working with. Apparently they will pay for themselves by way of greatly reduced electricity bills. Having seen my employers electricity bill I fully understand why they have done it but I'm not sure they factored in maintenance. .

Oh dear - that's not good. Sounds like you've been dealt a raw deal. And one of the key features of LED is that they're meant to be maintenance-free (no more expensive scaffold platforms to change a light bulb!). I hope your employer kept the receipt. I hope even more that they aren't my lights......

Paul

[JamesF]

First off is the extraordinary quote from the IDA: "This now puts us in the awkward position of opposing a brand-new lighting technology that promises substantially lower electricity use and cost savings.". Now some of the fixtures that we manufacture have received the "Fixture Seal of Approval" from the IDA. I pay $250 for each fixture and an annual renewal fee of about 10% of that. The IDA state in their blurb about the FSA that colour temperature of LEDs is a concern for them (see here: http://darksky.org/fsa/)but they're still prepared to take cash from me and give my lamps an approval, despite also saying they oppose LED lighting in the quote above. I'm sorry, but that strikes me as inconsistent at best.

Others might quite understandably describe it as appearing to be blatantly hypocritical if they continued to take payments for such lighting when they claim to be opposed to it.  I certainly don't think it would be unreasonable to expect the IDA to explain the apparent incongruity of these two issues and what they intend to do as a result.

James

[Paul M]

Oh dear - that's not good. Sounds like you've been dealt a raw deal. And one of the key features of LED is that they're meant to be maintenance-free (no more expensive scaffold platforms to change a light bulb!). I hope your employer kept the receipt. I hope even more that they aren't my lights......

Paul

My first observation is that the floodlights haven't had any thought put into them. Many of them facing out almost horizontal . The car par area is particularly dazzling. 

A number of them seem to have failing drivers as they constantly cycle on/off.

Much of the external lighting was 28w 2D bulkhead fittings which were retrofitted with LED trays. No shielding!

The indoor IP56 twin fluorescent fittings were retrofitted with LED tubes and drivers. Perhaps the decision to retrofit was a bad one. Failure rates are high.

It's poor lighting design at it's best, or do I mean worst?

[mapstar]

LED's on my street have improved the intrusion into my garden considerably. Visual astronomy is miles better although not being from the dark side I wouldn't know about imagers.

Damian

[Psychobilly]

Driving through the lanes fitted with them tonight the headlights on the disco we totally washed out by the streetlights but the pools from  the streetlights  didn't overlap so you were going form "daylight" to headlights and back again all the time....

I am not anti LED I use a couple of million a year in a few products we manufacture... and  the house lighting has been converted to LED (direct bulb replacements) ... Instant on , nice lighting can't complain...

Perhaps I just need to buy a few million gallons of blackboard paint  and a crop sprayer and paint he whole of the ground around here with it

It's certainly worse for imaging which is what I do (or rather did) ...  Now there are gradients all over the place where the IDAS filters just got rid of that lovely Sodium Orange Glow and let me take long exposures until my hearts content...

Peter...