by Barbara Clowers
We promote responsible lighting design based on the principles of balancing the need for light at night with human health, environmental health, and preservation of nature, including the night sky. Elements of responsible lighting design include:
- eliminating waste which includes saving energy and reducing greenhouse gases
- capping total lumens to control light pollution,
- employing fully shielded luminaires in most applications,
- mitigating or eliminating glare,
- using lighting only where it is needed,
- choosing the proper color temperature and spectrum of light,
- eliminating over lighting,
- dimming or shutting off lights when not in use
- establish a verification and accountability process using suitable metrics
- produce an attractive outcome.
Problem: Health Risks of Blue-Rich White Light (BRWL)
- Exposure to blue-rich white light (BRWL) resets our circadian clock in the morning making us alert. The circadian clock is reset again at night by an absence of BRWL stimulating the production of melatonin and fatigue resulting in sleep. Exposure to BRWL at night disrupts circadian systems in humans and all other living beings with detrimental impacts.
- Exposure to BRWL inhibits the production of melatonin. Reduced melatonin production has been scientifically linked to human breast cancer, metabolic syndrome, diabetes and other diseases.
- In 2012 the AMA stated nighttime light exposure is hazardous human health and has potential tumor-enhancing effects related to melatonin suppression, especially for breast cancers.
Violation of Davis Dark Sky Ordinance 1966
The new LED street lights violate City of Davis Dark Sky Ordinance 1966, passed unanimously in 1998, creating standards for outdoor lighting which mitigate light trespass, reduce pedestrian glare and limit light trespass. That ordinance was passed to:
- Minimize light pollution, glare, light trespass caused by inappropriate or misaligned light fixtures and preserve the night sky as a natural resource and people’s enjoyment of looking at the stars.
- Restrict any light dispersion above the horizontal plane from the lowest light emitting point of the light fixture.
- State that any light emitting lamp, or luminaire lens, shall not extend beyond the shielding of the fixture and be fully shielded.
It contains the following definitions:
- Light pollution shall mean any artificial light which causes a detrimental effect on the environment, astronomical research and or enjoyment of the night sky, or CAUSES UNDESIRABLE GLARE OR LIGHT TRESPASS.
- Light trespass shall mean artificial light that produces an unnecessary and unwanted illumination of an adjacent property.
- Glare shall mean artificial light that causes annoyance, discomfort, or loss of visual performance and visibility.
We contend that the newly installed LED street lights violate the letter and/or intent of Ordinance 1966 in all of the following ways.
- Although “fully shielded” against uplight, the blue rich white LED light source and luminaire design currently installed, pose detrimental effects in several areas by emitting significant light in the glare zone (above 70 degrees relative to nadir) which in turn causes light trespass into residential windows and causes disability glare for pedestrians. This is in direct violation of City Ordinance 1966 which provides for limiting and/or prohibiting light trespass on an adjacent property and the restriction of light quality which poses glare hazards for pedestrians and motorists.
- Established peer review scientific research has demonstrated that excessive blue spectrum component of LED radiation, similar to that of the light source installed in Davis, has a number of potentially significant and deleterious impacts on people and the environment. In summary these include:
- Increased artificial sky glow due to increased Rayleigh scattering in the atmosphere. Here in Davis, independently documented collected data establishes a 14% increase of sky glow directly attributed to the replacement of the older high pressure sodium streetlights with the newer LED street lighting. This type of light further limits the enjoyment of the night sky and dramatically limits the suitability for astronomical research.
- Excessive glare from lights, as a function of spectrum and source luminance, can cause temporary blindness and excessive discomfort and disability glare in all ages. Glare results in decreased visibility at night for persons over the age of 42 (causes age related disability glare) and promotes longer periods of light/dark adaptation for senior pedestrians and motorists alike.
- Blue light in particular has detrimental effects on human health, and on plants and animals, as well. Extensive and well established scientific research over the past two decades shows that natural biorhythms are set by exposure to the blue frequencies in white light, and exposure to these frequencies at night interferes with and alters the biorhythms of humans, plants and animals.
Action:
As publically stated and privately expressed previously by a number of concerned citizens, including the professional opinion of lighting experts living in the community, we believe that the necessary actions to remedy the situation include:
- Install new LED luminaires with improved shielding equal to the “flat lens cobra head” of the high pressure sodium predecessors: new luminaries must feature glare shields that prevent light trespass onto homes and reduce glare potential for motorist and pedestrians.
- Replace all installed LED streetlights with the following: Residential areas to provide for high CRI ( > 85 ) 2700K with photometrics providing for less than 10% of the radiant energy in the blue spectrum( 430 – 490 nanometers). Roadway areas to provide high CRI ( >85% ) 3000K light source with less than 10 % of the radiant energy in the blue spectrum.
- Eliminate the cobra head style of luminare and limit the spectrum to blue-free amber light sources for path lighting, bikeways, parks, pathway, greenbelt, and other environmentally sensitive areas. An alternative light source to include filtered white LED’s (<2000K) with zero emission of blue spectrum below 500 nm. As in current and established practice throughout US National Parks, we also recommend “indirect” design style luminaires for either the LED or blue-free amber light sources.
- Establish a committee to measure, monitor, advise and report on light pollution, total lumens and energy consumption. This committee must include representatives from the following groups:
- A representative familiar with visual needs of an aging population.
- Persons engaged in astronomy and other aspects of nature appreciation and preservation that are related to dark skies.
- Experts in the lighting science, independent of industry
- Establish a process for street light removal when requested by the residents concerned. Currently, once installed, a street light can never be removed. Excess lighting can be wasteful, unaesthetic, reduces property values, can reduce visibility, and affects human health and the environment.
Barbara Clowers is a long time resident of Davis, former owner of an “innovative” small business located in Davis, parent of grown children, member of the International Dark Sky Association, cursed with six unshielded street lights and married to an amateur astronomer who enjoys astrophotography.
Dear Readers, I don’t think this is over most of the folks here in Davis but “it’s too technical for a general-interest newspaper like The Enterprise”. I wrote them a letter to the editor that used the Three Bears to make my point.
I don’t want to say definitively until I see the staff report, which we may see today. However, I believe the City chose what I believe to be the highest quality fixture among the seven available for evaluation as test lights for the survey, and apparently they also use less energy.
The idea of shutting off the greenbelts at night will not fly, even in a town like Davis. There are people out at all hours. I bike the greenbelts late at night, sometimes in the wee hours, and people use them. I love the darkness and am annoyed by blue-white light, but darkness on City transportation corridors won’t fly politically or for safety reasons. There were two blue-white test lights and two yellow-white test lights for greenbelts. While no decision has been made, either of the yellow-whites would be acceptable, and I can’t imagine from the way things are going the blue-white would be chosen.
I was rather shocked in recent visits to Berkeley, Oakland and Palo Alto that these so-called progressive cities have gone to blue-white light as their night-time standard. Davis may lead the way in this one. This an example of Davis working. Sure, it would have been better if the research was done in advance, but sometimes staff doesn’t see the problem up front. The City Council paused the program, staff responded, and it appears a solution suitable for most-all has been reached. At this point I hope we can support the City in this general direction, and work on the detail to comply with dark-sky ideas as we go. There’s a lot I’d like to see, but getting the light-frequency right and the glare reduced on the residential lights is 80% of the solution. Applause to Council, staff, citizens, process.
I hope that we can get some press on this, the issue, the complaints, the research, the solutions. That could place Davis as a positive innovator as other cities look to replace their streetlights with night-friendly versions of LED lamps.
Alan, I can’t find staff reports on the city website, can you give me a clue where to find them? I thought it should have been posted two weeks ago when street lights were on the agenda but it wasn’t. Or I could not find it. I even emailed and asked for it but got no response. The the item was taken off the agenda about 10 hours before the meeting. How far in advance does the city have to provide the report? Seems like it should have been available the day of the meeting but I could not find it.
DBurns, As of 1:30pm the agenda for Tuesday had not been posted (seems pretty late), so no associated reports. Last time there was no report as apparently there was a meeting on Monday that could change the outcome for Tuesday, and at least one Councilmember I spoke to found that a troubling precedent, to schedule the item without the info available in advance, and ultimately the item was pulled. I thought all information had to be posted the Friday before a meeting, but apparently that is suggested, not required. I’m informed the issue will be on Tuesday’s agenda
I was also informed that the light chosen is “similar to” the one preferred by the public, but with an even warmer frequency. That is good on its face, and I am looking into confirming if this light can be mounted for comparison before Tuesday, and just how similar the light is. Other characteristics that were of concern were the high-glare at approach angles that the preferred light minimized, and the number of diodes, which in the examples we viewed the more smaller diodes produced a better quality of light, also seen in the preferred fixture.
We are all for energy savings and reduction of greenhouse gas, but the myopic viewpoint of the City action with LED street lights is a mistaken policy gone badly wrong. My house has six street lights shining in my windows. About seven years ago, at our request, the City changed the old dropped lens High Pressure Sodium (HPS) with full cut off cobra head HPS fixtures. On May 26 this year, they removed all the full cut off fixtures and replaced them with the new LED glare bomb wonders. There is no longer any cut off and my bedroom is brighter than a full moon. Facts the City did not tell us (and possibly did not know)- The peak energy wavelength (445 nm) of the new LED lights is a match for peak human sensitivity to blue light at night (460 nm) which is directly linked to serious health effects via disruption of circadian systems- The high energy efficiency rating includes the light in the 60 to 90 degree range which is mostly glare. In effect, we rate these new LED lights by including the portion of the light that formerly was shielded. – Glare is particularly disabling to aging citizens and should be considered a safety issue. Generally, we need better contrast to see better. Brighter lights, especially those with glare, more often make seeing worse.- Measurement of sky darkness increased 14% after May 26. This is a significant reduction in ability to see stars or anything else in the sky at night.- Measurement of a new LED showed that it has a significantly higher CCT value than the 4000 K told to the public (4812 K)So what could have been done? We could have tried to comply with the existing lighting ordinance passed unaminously in 1998, especially with regards to issues of light trespass and brightening the night sky. We could have done a little more homework and found that efficient LED lights are available that address the human health issues. We could have reviewed the lighting practices — for example why do I get six street lights when some citizens I spoke with are glad to get one street light on a whole street. We could have discussed the fact that many cities, when faced with the same budget constraints, found that they could save money with lights just by reviewing actual need by location and time and turning some lights off when & where not needed. We are all for energy savings, but we must consider more than one single issue in isolation.
A possible relationship between blue-white CCT artificial lighting at specific frequency ranges, light intensity and health effects has not been definitively established. I would like to see a link to appropriate studies if possible.
Night time in Davis is far from being totally dark. If all sources of artificial light were to suddenly vanish one midnight in Davis there could be two sources of natural light for vision.
The strongest natural source of light at night is moonlight. Moonlight varies widely in intensity by the phase of the moon. Moonlight is natural light from the sun reflected by the moon. The color of moonlight exhibits warm tones when the moon is low in the sky, dimmed by a lunar eclipse or filtered by air pollution. Moonlight is a cold light in most instances. Thus, the dominant source of natural light during night is blue-white in color.
Sky glow will vary in color. The source of natural sky glow can be starlight, moonlight, refracted sunlight, lightning and a few other natural causes. But, for most Davis suburban dwellers visible sky glow is produced by artificial lighting (light pollution) from their community, nearby communities and their geographical region at large.
The third and weakest form of natural light at night is starlight. When viewed by the naked eye individual stars may produce all colors of the visible spectrum. However, the intensity of starlight is so weak that it provides extremely little illumination of terrestrial objects and what starlight that may be available is seen as a blue tinted light due to the Purkinje effect.
The sensitivity of human vision is shifted to the blue end of the visible spectrum in dim lighting conditions such as natural light at night. This is the Purkinje effect. This is why humans begin to loose color vision after night vision activates. Eyes exposed to naturally dark conditions will exhibit full night vision after about twenty minutes. Purkinje effect is why moonlight appears bluish even at a full moon.
How does this relate to LED street lighting?
I live on a residential avenue in North Davis. My housing tract was built in the late 1970’s and was equipped with high pressure sodium street lights. One of these street lights stands at a corner of my property. You have all seen HPS streetlights. These produce a fairly diffused orange/pink light that looks like no natural light that may be found at night anywhere on the planet with the possible exception of the Kilauea volcano during an eruption.
Our HPS streetlight was replaced with LED lighting this summer. I found that the amount of light reaching my house was a bit excessive with the new LED array. This is known as light trespass. Too much glare and waste light entered the house. I also found the stronger light detrimental to my longtime backyard hobby of sky watching with 15×70 astronomical binoculars. I contacted the City of Davis and they made some modifications to the LED streetlight that were much to my liking. Siemens has a relatively inexpensive modification available to greatly reduce LED light trespass. I no longer see bothersome glare and waste light intrusion in the house. The backyard is now actually darker than it was when the old HPS streetlight was installed. The LED light now reaching my house is similar in color and weaker in intensity to the light of a full moon.
The LED streetlight at my house is one of the less intense blue-white arrays. I prefer this bluish light to that of the warmer-toned LED arrays because it looks more like natural light at night. The blue LED light looks more like moonlight than the warmer LED light, which resembles daylight. Daylight during night is not a natural condition in my experience.
I participated in the LED residential/greenbelt streetlight demonstration and survey conducted by the City in August. This community outreach effort made quite a variety of LED lighting arrays available for comparison. The assortment of Siemens LED fixtures produced light that varied quite a bit in CCT (color), intensity and other parameters.
LED streetlights produce more glare when looked at directly than older generation streetlights but I tend to avoid looking directly at streetlights at night. I find glare to be more of an issue with lower mounted greenbelt lighting LEDs than with residential and arterial LED streetlights that are mounted on taller poles. Older residents will be more uncomfortable with LED glare than the younger. Siemens has ways available to reduce glare from LED lights.
As mentioned, I have a preference for some of the more diffused and slightly blue-white LED streetlight colors as these produce a hue that is close to that of natural light at night. I suspect that most Davis residents will show a preference for warmer hued LED streetlights because they look prettier. The warmer LED streetlights do the best job of bringing out the colors of vegetation and painted or colored materials on Davis properties. I’m betting that most Davis folks will prefer a more artificial-looking light simply for the more vibrant colors it will produce in their neighborhoods at night. I’m fine with that.
1lux of light
Initially, it was thought that bright light, at least 2500 lux, was required for melatonin suppression in humans.[31] More recently, however, it has been shown that, under carefully controlled conditions, retinal exposure to illuminances of as low as 1 lux or less of monochromatic light at wavelength 440 to 460 (blue-appearing light) can significantly lower nocturnal melatonin,[32, 33] as can <100 lux of broad-spectrum fluorescent light.[34-37] These same light levels can also elicit significant phase shifts of the circadian clock and directly enhance alertness[37-40]; approximately 100 lux exposure will cause about 50% of the maximum response. Such light exposure, when experienced in the evening at home from bedside lamps, TVs, computer screens, tablets, and other devices, causes suppression of melatonin, delays the timing of circadian rhythms, and elevates alertness, all of which make it harder to fall asleep, make it harder to wake up in the morning, and restrict sleep.[36, 41]
I can find the article this came from with a little effort. Bottom line, it doesn’t take much light to effect melatonin production.
So, to avoid sleep and melatonin disturbances that could adversely affect health you should completely duck tape and shutter your bedroom against the light of the full moon, which can produce 0.27 to 1.0 Lux of bluish light. Don’t forget to turn off all lights, TVs and smart phones after dark.
I do have a house filled with colored light, as well as yellowish-white light when needed, almost all from pleasant LEDs. I sleep like a log. Getting up, however, requires CAFFEINE, not LEDs.
Moonlight is by nature entirely reflected light, you can look at the moon without squinting due to glare, moonlight produces a distinct shadow, and reflects well into darkened areas.
When evaluating the streetlights, we found all the blue-white, and some of the yellow-white lights produced a harsh glare, especially at particular approach angles. Those especially with fewer but larger diodes produced strange, grid-pattern shadows. Most important perhaps, we noticed the blue-white light didn’t reflect hardly at all. Thus, behind dense vegitation or under a tree canopy, it was almost completely dark even near a blue-white array.
Moonlight, though it may have a similar light frequency, lacks these other harsh traits of the blue-white LEDs. Though a shield may have helped with the blue-white light reflecting into your house, what disturbs me about the current blue-white LEDs is riding under them at night. I use a baseball cap now if I have one with me when biking at night to minimize glare from above. When driving in a blue-white LED area, I now use my sun visor for the same purpose.
It has been mentioned that older persons have trouble with glare and I think this needs to be explained further. When older persons get cataracts or glaucoma, it is often harder for them to drive at night, partially due to distinct light points turning into diffracted beams, like looking through a dirty windshield covered with droplets of tree sap. Glaring light is particularly difficult for people with these ailments to deal with, as it produces even more refracted beams in such compromised vision.
I do appreciate that you like your blue-white light. It is a personal preference.
I am 61 years of age and have been blessed with good vision. I wear only reading glasses for close-up vision. My brother was a sharpshooter and an airline pilot. Good night vision is one of the better genes running in my family. We all have better or lesser genetic traits related to survival.
Night vision can be reduced significantly with age owing to the time required for the iris of the eye to respond to changes in light intensity. Some older people retain night vision longer than others. With people who loose night vision early the iris fails to open fully and quickly to low light conditions. The response to brighter lighting condition may also suffer. This can result in problems with glare. It can happen at the age of 30 or at the age of 70. Cataracts and glaucoma can also contribute to problems with night vision.
Basically, if you have problems driving along streets illuminated by LEDs then you also have problems with automotive headlight glare. It comes with age, unfortunately. We all have to deal with it given time.
“if you have problems driving along streets illuminated by LEDs then you also have problems with automotive headlight glare.”
True.
I have no problem so far with headlights that are correctly aimed, regardless of light emitter type. If poorly aligned LED or HID headlights are blinding worst-case scenarios for me, I want to shoot them down.
So far no citizens have shot down any glaring LED streetlights (that I know of).
We can all take responsibility for turning off the lights we control including cell phones, computers, and tvs but the light the city provides should not shine in our windows. That’s why we have a dark sky ordinance. The light the city uses in public spaces should not be in the blue-rich white spectrum. The point of this retrofit was to save money and reduce greenhouse gases. If I have to close my windows and turn on the air conditioner because of the lights it is just shifting the cost from the city to the individual but it doesn’t reduce greenhouse gases.
Update: The Staff Report on the Streetlights is due to posted this evening (Fri) some time after 6:00 p.m.
Tnx.
Alan, I can’t find it. I’m on their email list. No email. Spoke with Mitch around 2 PM.he said the emails would go out today and he would send me the staff report. Very frustrating.
Excellent article and comments here!
Great to bring the science evidence to bear on choice of lighting. Kudos!
Staff report has been posted:
http://city-council.cityofdavis.org/Media/Default/Documents/PDF/CityCouncil/CouncilMeetings/Agendas/20141021/09-LED-Streetlights-Update.pdf
If anyone at the City is “listening”, it would be very useful for those of us who took the light survey if the table could be revised to contain the light numbers from the survey, as we do not have a cross-reference to the names of the lights referenced in the table.
Just got the staff report. Their snafu cost us $325,000 and they say the new fixtures will be a warmer color of 2700K. The last Leotek glare bombs were sold to us as 4000k but independent test shows it to actuall be over 4800 k. Maybe thes will be sold to is as 2700k and will actually be closer to 3500K.
They did not address the color spectrum at all. See the chart above. These lights may be better, I believe they were in one of the 2012 demo sites BUT their glare rating is the same as what we are removing.
In terms of energy conservation, this is picking the low hanging fruit. They could do much better but there goals are very limited. We need a leader who sees the big picture like Julie Partansky.
The full moon provides pretty uniform, albeit very low fc (foot-candle) lighting, but is perfect (pretty much) for most non-motor vehicle nighttime lighting tasks. Works well with the human eye (if ‘normal’). For years, street lighting in Davis was “focused” on illuminating intersections of streets (where bike/ped/motor vehicle conflicts are most likely to occur). Then there were spacing standards adopted, based on ‘spacing’ along non-arterial streets, as well as spacing on arterial streets where due to higher speeds, objects within the roadway are a potential issue.
If all vehicles (including bicycles) have functioning lights, and if bicycle riders and pedestrians wore light and/or reflective clothing, street lighting levels would be less of an issue.
Some citizens want the night to be as bright of day… they cite security, “someone else has more lighting than I do”, or other BS concerns. Although I feel they should be dismissed, they tend to be very vocal with staff & electeds. Then we have the idiots who plant trees adjacent to street lights. Duh. [side note: good reason for good communication/shared values between PW/tree lovers/planners].
Even, consistent lighting is valuable. Lighting spectrum issues I’m not so knowledgeable about, but I know LOW pressure sodium lighting was not only less energy efficient than HPS, but also made it almost impossible for first responders to distinguish blood from motor oil at the scene of a vehicular crash. “Color temperature” is important, but I do not ascribe to the author’s characterizations. Not within my ken.
Low sodium light is so bad at color rendering, it is mentioned in the dark sky ordinance. It specifies it cannot be used exclusively–gotta be in conjunction with another type of light for color rendering.
I agree full moon light provides plenty of light. Wish more people felt the same. Almost everyone agrees to streetlights on corners, crosswalks and points of conflict but that last one gets tricky. A curve is considered a point of conflict. That is why I have 6 lights that shine on my property. I live on a corner and both streets that intersect are slightly curved. Each curve gets a light, then 300 feet from the corner there is another light. Because of the curves and the location of my two story house all six shine on my property. There is no evidence that the extra lights prevent accidents. The curves can be marked with reflectors, a white line on the street and a yellow sign that says ‘curve’ yet there is no process to evaluate the current placement and efficicy. The developer installed these lights in about 1966. There is no review process to remove unnecessary street lights. At the neighborhood pot luck I heard of a house that has a street light located IN the driveway! It is located a third of the distance from the one edge of the driveway.
We have a similar situation with our intersections. Near me there is a T intersection with eight lights. If I count the adjacent lights that are less than 300 feet from the intersection I get nine or ten. Downtown intersections have four lights.
Many people we have spoken with are happy to have one streetlight down the block from their house and can’t believe we have six because it is not common or necessary.
Regarding consistent lighting, California and many other places strives for consistent light on the pavement. Frankly, trying to consistently light residential streets is insane! We need lights to help us recognize intersections and the end of cul de sacs bit we do not need every foot of the pavement to be lit! Our eyes function best in the dark with contrast so overlapping ovals or pools of light with some darker areas between the lights is actually better. This does not mean very bright pools of light under the street light with very dark shadows between them like we now have, due to the brightness of the current LEDs and the light being blocked by mature trees. Dimmer lights will decrease the contrast and make the shaded areas appear less dark because (we hope) our eyes won’t constrict so much under the light and we will retain some dark adaptation as we move into the shadow.
According to staff report issued 10-17-2014:
http://city-council.cityofdavis.org/Media/Default/Documents/PDF/CityCouncil/CouncilMeetings/Agendas/20141021/09-LED-Streetlights-Update.pdf
The LED street light array installed on the corner of my property is one of 13 “cooler temperature” (blue-white) LED fixtures that was equipped with light shielding on special request. This installation will remain in place.
According to page 2, paragraph 6 of the above this LED light will remain in place unchanged. “The Arterial and Collector level roadways would continue using the cooler temperature LED cobra head fixtures that have already been installed. In addition, light shields will be used to address specific, localized issues related to light spill into residences. Shields have been installed at 13 locations in various neighborhoods to address specific light spill concerns and have generally been well received. Criteria for their installation will be developed.”
Otherwise, the selection of lower temperature (warmer) LED arrays for Davis residential streets follows the outcome I suspected and described earlier in this commentary.
If you enjoy binoculars and the night sky, the current LED lights will impact your view of the night sky more than the proposed 19 watt 2700K lights. The peak of blue light is problematic for night time viewing. Blue spectrum light scatters more in the atmosphere (as well as in aging eyes). Anywhere there are astronomers, they work hard to minimize blue spectrum light at night.
I can count about 25 to 50 stars at night now. Anyone else want to give that a try? I have read that to feel the wonder of the night sky, one needs to see about 450 stars. Some guy was interested, did a lot of work and came up with that number. I am always amazed that the stars are all there and all we have to do to see them is have a power outage. During the 1994 Northridge earthquake, TV, radio stations and police were bombarded with calls asking what the strange lights in the sky were…did they cause the earthquake?…was there an alien invasion? No, folks who had never seen the Milky Way were just getting their first and possibly only view of that awesome light in the sky.
If you live on arterial or collector streets and don’t want the blue lights, you should attend the next city council meeting.
DavisBurns, your suggestion is a good one. It would be interesting to learn about what the night sky looks like for other Davis residents. Tonight is forecast to be mostly clear with cloud cover increasing to partly cloudy on Sunday night. A waning crescent moon will not rise until 3:20 a.m., so the moon won’t get in the way of things earlier than that.
I’ll be out looking tonight and will give my eyes a full 20 minutes to acclimate to night vision prior to making a naked eye survey. To be honest, I’m going to see a great many more stars than 25-50 from my backyard.
It’s safe for me to tell you that I live on Grande Avenue in North Davis. I believe that the city considers this a connector street. Grande has wide bike lanes on either side and sidewalks but the vehicular roadway is actually quite narrow. Our neighborhood group has been successful in having the City install several traffic calming measures on this 25 MPH street.
There is a 54 watt LED array in front of my house. The next closest street lights are too far away to be any problem. I describe this array as medium blue-white. The LEDs in this array are arranged in a six-cluster pattern. The city installed a light shield on this lamp at my request. The shield is a black “waffle” that provides very effective cutoff of LED light at a distance of about 10-15′ back from the sidewalk. What this shield does is block a direct line of sight to the actual light emitting diodes, eliminating glare. Some diffused LED light does reach the front of the house but I would guess that the strength of this light is only 10% of what it was before the shield was installed. I’m also seeing only small fraction of the light I used to get from the old HPS lamp. I see much less light trespass on backyard trees than I did with the HPS streetlight.
I would rather take my chances with the shielded 54 watt cold than an unshielded 19 watt warm LED.
As far as dark sky quality goes for Davis: it is not that good and on par with the rest of our region. I frequently watch stars while anchored out on sloughs in the middle of the central California Delta 35 miles SSE of Davis. There aren’t any streetlights within miles of that place and the night sky is only marginally better than Davis.
I vacationed at Sea Ranch last month where there are no street lights at all. There are no sidewalks, either. The star gazing was spectacular before the night time overcast moved in from the ocean. It’s not fair to compare Davis to Sea Ranch, though. For one thing the building density is much less and so is the traffic.
I will report in tomorrow regarding tonight’s sky watching.
I believe you can also get the new lights shielded should there be a problem.
Alan, while no one has shot out a street light as far as we know, it is amazing how many people respond with that desire. One of the city council members did–Joe Krovosa I believe–and LOTS of people I talk to. It seems to be how we feel about it at a gut level. Being civilized, as such statements come with a caveat–of course, I really wouldn’t…
DanH–you might be interested in stopping by Explorit on October 23 to see the partial eclipse of the sun in the afternoon. Lots of telescopes set up and folks of all ages. Actually, everyone is welcome.
Speaking of finding dark places, the nearest place we have found is Cowboy Camp on highway 16 headed to Clear Lake. There are places you can camp and still have a good view of the heavens. You can see the Milky Way. The local astronomy club has a place they meet near a small airport in Blue Canyon east of here but its a lot longer drive. More and more, dark sky locations are a vacation destination with the National Park Service working hard to put on programs (half the park is in the dark) and keeping light pollution to a minimum.
Predictions are there will be only a few isolated places in the America with dark skies in 20 years. Light pollution increases every year across the world at an average of 6%. Predictions are that trajectory will continue and may actually increase because of the introduction of energy savings LED technology. Of course, if you save 50% on electricity and put in 100% more lights you aren’t actually saving anything. The lighting industry is the only industry known that has spend the same percentage of GDP over 3 centuries, 6 continents and 5 technologies. They have a 100% rebound effect.
The city says it will install shields on the soon to be installed lights but I think you are on an arterial street and couldn’t get one of the new lights if you wanted it, so good thing like what you have. Personally, I don’t see why they don’t take the 27 (or 29) watt Leoteks installed on residential streets and reinstall them on feeder streets. After all, it is obvious the sold us higher wattages than we need.
I looked at the sky from our North Davis backyard last night. My little backyard allows viewing of perhaps 25% of the full sky owing to blockage from tree plantings and the house itself. I did a quick star count with unaided eyes at midnight and tallied at least 400 stars before quitting. The Pleiades star cluster and nine of its brightest stars were easily seen. I usually can’t see the Andromeda galaxy unaided in Davis and last night was no exception. It was almost at the zenith last night and very easy to observe by lying on my back with Oberwerk 15×70 binoculars.
The star viewing in Davis is miserable compared to that of darker skies in Northern California. It isn’t as bad as sky watching in the Sacramento or Bay Area regions if that’s some consolation. The dark sky ordinances in Davis are a joke. These laws are on the books but the city remains vastly over lit at night. I’ll blame this one on the lawyers. It’s just too easy to hold governments liable when bad things happen in the dark and artificial lighting is cheap and easily obtained.
The new shielded LED streetlight in front of my house didn’t make viewing any worse than it was with the old HPS streetlight. It is a little better, in fact.
Don’t blame the lawyers on this one. It’s the politicians. The public safety mantra is just like mom and apple pie. Humans have an Inate fear of the dark so it is drop dead easy for any elected official to receive approval when the words more light and public safety come out of his mouth. Advocate less light and you lose votes.
The courts are clear that we have no obligation to provide street lights. We will win any suit brought against us for failing to provide light however if we install a light and do not maintain it and someone is hurt we are then liable.
Good seeing last night. I could see the Pleiades and more stars than usual. Not bad tonight either. Enjoy it this year because next year and every year after it will become steadily brighter.
I went out at 1:30am last night and checked out the new recommended warmer-frequency streetlight.
I believe we have a winner.
My survey choice was #6, as was the community choice in the survey. This new staff recommended lamp, unmarked but the next light west of #8 on the opposite side of the street (has a neighborhood watch sign on the pole), is the same as #6, except the diodes are shifted another step into the yellowish light spectrum. This is great, as I found #6, though the right spectrum, was a bit too white in the yellow-white. New test recommended bulb is otherwise identical to #6, so this new one is a winner in my book.
I do believe in the next few years even better streetlights will come on the market, possible similar technology to the phosphorus used in Philips Indoor LEDs, and that cuts glare. However, #6 had the least glare, this also has the least glare, and you can stare at these diodes–though bright they do not require averting your eyes like the blue-lights, which have a much more intense glare that you can’t avoid even by not looking at them directly.
The new choice may be the best on the market now, it has less glare, reflects dispersed light well, has multiple diodes which gives a more distinct light dispersion, and is at least as bright as current sodium streetlights.
I believe in dark sky principals, I also think we need streetlights. I am not thrilled this is going to cost an extra 1/3-million, but the alternative would have been the City didn’t listen to the citizen objections and just finished the program. I prefer to live in a City that admits its mistakes, and I thank both Council and Staff for the fine work of pausing, testing, surveying and coming up with a winner.