Does the glow of the sky or the glare hurt more? - Light pollution - Cloudy nights (2023)

Tony Flandes

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There are two types of light pollution: sky brightness and glare. Skyglow descends from the sky. Artificial sky glows are usually caused by lights that are quite far from the observer, often those that are completely invisible from the observer's location. The light rises into the atmosphere and is then scattered towards the viewer by various particles in the air or by the air molecules themselves.

Glare is light shining directly at you, or perhaps at a nearby surface that you can inevitably see. If you live on a street with lights, those lights add essentially nothing to your skylight, but they can make astronomy miserable in two basic ways. First, glare tends to get into your telescope, camera, or whatever. It can be partially blocked with good shielding and lots of light-absorbing surfaces, but only partially. More importantly for visual observers, it is impossible to maintain good dark adaptation when lights are shining in your eyes.

In general, my experience is that sky brightness is more of a problem in dark areas than glare, and glare is more of a problem in bright areas. In my country house, for example, glare is not a problem. I have to stop my work when a car goes by, but that usually only happens once an hour at night. And I can see two houses next to me, but both are separated from me by hundreds of feet of woods, and neither have really ugly lights. However, the artificial skylight is a real problem. I usually get SQM readings around 21.0, which means that the artificial skylight is stronger than the natural sources, even at the zenith, and much stronger to the east and west, the directions of the main light sources. I can still see the Milky Way easily, but that's really a very low bar. I lose a lot of detail inside the Milky Way and when looking at other galaxies through a telescope.

Ironically, the artificial skylight is not my main problem in my city house, even though it is at least 20 times stronger than in my country house. Instead, my biggest problem is finding a place that doesn't have lights shining directly into my eyes. One sidewalk is out of the question because of the streetlights. The church parking lot across from my building is fine for planetary viewing, but not deep sky astronomy. I have explored almost every open space in the city (Cambridge, MA). No one is really immune to glare, and few have ranges far enough from the lights to do deep-sky astronomy. And that's in a city with fairly strict lighting codes that are actually enforced, and with a culture that has frowned on ostentatious display since the city was established in the early 18th century. I'm sure most American cities of the same size are much worse.

And you? Both skylight and glare are problems for most of us, but which seems to be a bigger problem for you?

Edited by Tony Flanders, Jan 26, 2023 - 11:40am.

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unity lover

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It shines all the way. Bortle 8 showed m 15 very well, and the glare makes it impossible to see even from Bortle 7.

dnayakan

Wostok 1

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My experience matches yours.

There's a way to be worse when dealing with glare, especially when it's intermittent (e.g. passing cars, looking through the eyepiece at a streetlight, etc.). It wreaks havoc on my dark adaptation: the sky glow allows my eyes to settle to a decent point and no violent fluctuations after that, while the glow prevents my eyes from really settling and looking set, pupils doing smaller etc I know this because when I'm primarily concerned with the skylight and someone shines a flashlight, I start blinking, which I think is the body's response to using the eyelids and not the pupil (because the dark-adapted state can't respond to a rapid rise). light flow as fast as closing your eyes).

So in general I would prefer to choose a higher sky brightness than a glare because I tend not to react to glare.

bye dj

Rasfahan

Vanguard

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Both. I'm in Bortle 5 on the clearest nights but when the humidity rises it can be as high as 7. Also, all my neighbors believe that flooding their patios with reflectors pointing in different directions (even up) increases safety. I started covering my head with a dark cloth over the eyepiece and even wearing sunglasses when I need to capture something from the "outside". Interlaced, but it helps a lot against glare and allows me to maintain dark adaptation.

Alex Swartzinski

viking 1

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For me it's Skyglow. I only have a neighbor light to worry about. Leaves block it out most of the year, and an angled umbrella keeps it out in the winter.

Everywhere I have observed from there there is some level of distant skyglow in one or two directions. If it's low on the horizon, I don't care, but it would be fun to experience pristine skies in all directions.

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mike g

Mercury-Atlas

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Right now, Skyglow is my current nemesis. I do most of my observing from my deck in my backyard, which borders a tree line and then a farmer's field. the nearest light in that direction is about 3/4 mile away. My house and shed block street lights and lights from neighbors. Fortunately, none of my neighbors think they need extra security lights in their yard. However, my front yard is completely unusable due to the near glare from street lights. There are times when it would be really nice to use the driveway in front (so you can peek out earlier in the evening), but it's just not possible. We recently had a planned city wide power outage so I got up to enjoy what I thought we were going to have very dark skies. The sky turned out to be no different than normal as the hospital parking lot lights 2 blocks away were running on generators. I usually have Bortle 7-8 in my garden.

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bobzeq25

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There are two types of light pollution: sky brightness and glare. Skyglow descends from the sky. Artificial sky glows are usually caused by lights that are quite far from the observer, often those that are completely invisible from the observer's location. The light rises into the atmosphere and is then scattered towards the viewer by various particles in the air or by the air molecules themselves.

Glare is light shining directly at you, or perhaps at a nearby surface that you can inevitably see. If you live on a street with lights, those lights add essentially nothing to your skylight, but they can make astronomy miserable in two basic ways. First, glare tends to get into your telescope, camera, or whatever. It can be partially blocked with good shielding and lots of light-absorbing surfaces, but only partially. More importantly for visual observers, it is impossible to maintain good dark adaptation when lights are shining in your eyes.

In general, my experience is that sky brightness is more of a problem in dark areas than glare, and glare is more of a problem in bright areas. In my country house, for example, glare is not a problem. I have to stop my work when a car goes by, but that usually only happens once an hour at night. And I can see two houses next to me, but both are separated from me by hundreds of feet of woods, and neither have really ugly lights. However, the artificial skylight is a real problem. I usually get SQM readings around 21.0, which means that the artificial skylight is stronger than the natural sources, even at the zenith, and much stronger to the east and west, the directions of the main light sources. I can still see the Milky Way easily, but that's really a very low bar. I lose a lot of detail inside the Milky Way and when looking at other galaxies through a telescope.

Ironically, the artificial skylight is not my main problem in my city house, even though it is at least 20 times stronger than in my country house. Instead, my biggest problem is finding a place that doesn't have lights shining directly into my eyes. One sidewalk is out of the question because of the streetlights. The church parking lot across from my building is fine for planetary viewing, but not deep sky astronomy. I have explored almost every open space in the city (Cambridge, MA). No one is really immune to glare, and few have ranges far enough from the lights to do deep-sky astronomy. And that's in a city with fairly strict lighting codes that are actually enforced, and with a culture that has frowned on ostentatious display since the city was established in the early 18th century. I'm sure most American cities of the same size are much worse.

And you? Both skylight and glare are problems for most of us, but which seems to be a bigger problem for you?

image players Glow from the sky, no doubt. That's why I don't take photos below 45 degrees. Looking up, anti-dew, glare, glare is not a big problem. I rarely look through a telescope, my old eyes don't see much.

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Astrojensen

James Webb Space Telescope

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Glare is by far the bigger issue of the two here. I currently live in a small apartment in a village (5,000 inhabitants), on the outskirts of a medium-sized city (60,000 inhabitants), and the Milky Way is clearly visible to the naked eye.andYou can walk away from the glare.

Blue sky!

Thomas, Denmark

Sanbai

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I'm there with Tony.

I will certainly choose darker skies, even at the cost of some nearby light.

I have had similar experiences in state parks:

Two years ago I was in Chicot (Ville Platte, LA). It's hard to find a place without RVs or street lights with a clear view (no tree canopy). I finally found a corner of a parking lot above the boat dock. The bad thing is that there were bathrooms nearby that filtered some light. Despite that, and a well-hidden streetlight in the other corner, I had a great session, with a notable advantage over my (not so) dark side. At the end of the session I realized that I could have turned off the lights in the bathroom myself, because of me. During the last few sessions, there was no light in the bathroom and the nearby streetlight was also off. Unfortunately the splash zones and playgrounds are still lit up all night.

A stronger example.

Last November I camped at South Toledo Stake Park (Anacoco, LA), a place with even darker skies. One night the clouds disappeared. I hadn't explored the area before, so the only good place I knew of was the boat dock parking lot. Unfortunately, there was a white streetlight that I couldn't turn off. However, I had the best view of some objects. The quality of the sky was very easy to perceive in the eyepiece.

Unfortunately Chicot Park is a 2 hour drive and Toledo is a 3.5 hour drive. None of these are feasible for me for a one-night trip, only if we're going camping (and then astronomy is a side hustle that I have to de-prioritize). So for the regular monthly outing, I have to adjust to my not-so-dark side, which is only a 45-minute drive away. By the way, we are next to the embankment road and sometimes some cars pass by, but watching is better than at home.

I also had a really good experience at a driveway in downtown Flagstaff (AZ), it was better than my usual dark place in the country!

Even with dark adaptation broken, I still prefer darker skies even if there is some interfering light. I always carry a dark cloth to cover my head to block disturbing light.

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dnayakan

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Oh, one more thing. Where I live you have to drive ten minutes to get away from the glare. Getting to a location where the skyglow is noticeably lower requires many hours of driving (since much of the skyglow I experience is due to light pollution domes from various nearby cities). DJ

unity lover

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For me, my parents can take me to Bortle 5 in less than 7 minutes. Also, I got to see more of Philly in 20 minutes from my cousins' house than I did from my Bortle 7 house.

unity lover

viking 1

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I'm also fine with a low, warm glow. While in Bortle 5, the ~8 streetlights near the bathroom were warm and dim. They did not affect the observation of the meteor shower at all.

Edited by UnityLover, Jan 26, 2023 - 1:49 PM

Ron359

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One thing is for sure, all those looks locally add up to a brighter sky glow where there are few looks. You can't have one without the other, and therefore they are the same in any definition of light pollution.

For example, 10 separate smokestacks emitting clouds of sulfur dioxide and carbon soot cause high concentrations locally, but are equally responsible for degrading air quality over large regions as pollutants are "spread" or transported by our atmosphere. A good example was the Navajo Coal Power Plant in AZ and near the four corners. It was well documented, and studies showed that its emissions reduced visibility in many western states for several decades.

What some "experts" seem to forget in these "debates" is the basic physics of light. The Rayleigh scattering of short wavelength blue LEDs is 10 times that of longer wavelength unshielded sodium lights in LED streetlights. It's like removing 10 streetlights for each previous design. Not even all LEDs emit broadband continuous light. 10x local scatter means a 10x contribution to the brightness of the sky. And the intensity of the blue wavelengths is of the order of magnitude. higher than the lower wavelengths. Just look at the blue peak in this spectrum!

https://www.research..._fig2_299395983

http://hiperfísica....mos/blusky.html

Pollution diffused or dispersed in the air knows no limits. As they say in the real estate business; It's all about location, location, location.

Edited by Ron359, Jan 26 '23 - 4:17 PM.

steps

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One thing is for sure, all those looks locally add up to a brighter sky glow where there are few looks. You can't have one without the other, and therefore they are the same in any definition of light pollution.

For example, 10 separate smokestacks emitting clouds of sulfur dioxide and carbon soot cause high concentrations locally, but are equally responsible for deteriorating air quality over large regions as pollutants are "spread" or transported by air. our atmosphere. A good example was the Navajo Coal Power Plant in AZ and near the four corners. It was well documented, and studies showed that its emissions reduced visibility in many western states for several decades.

(Video) The Strange Scourge of Light Pollution

Airborne pollution has no limits.

Agree, the brightness of the high sky implies an inevitable glare. For me, low sky brightness means I can avoid glare, as low sky brightness means a low density area. For me, the sky brightness is the biggest problem, as it can take hours to escape, while the glare may only take 5-15 minutes to avoid if I'm in a low sky brightness location. Finding a public space in a rural area can be a problem, especially in New England where everything is forest.

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unity lover

viking 1

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It seems that my brightness in the sky is due to glare. (Unshielded LED, further south, more towns and fewer lights)

jorgeliv

Your information about light pollution

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Interesting thread you started here, Tony. The responses told me that some amateur astronomers have the same or a similar definition for "glare" and "skylight". One user, two posts up, wrote "...high sky brightness implies inescapable glare."

No matter what city you are in, the brightness of the clear night sky can NOT be dazzling under any circumstances. Unless a very low cumulus illuminated by local illumination enters your observing view, a prolonged blackoutsparklecannot have glare. I assure you that 17.0 and 18.0 mags/arcsec²(typical of big city nights) are dim glows. Imagine walking from a brightly lit room into a clear night sky and you'd swear the night is getting darker. But about a minute after your eyes have adjusted, you realize you're still in your polluted city. However, allconcentrated sourcesLights, such as street and porch lights, can be harsh depending on visibility and location. They may or may not cause the sky to glow.

The definitions should not differ from person to person. The clear definition of skyglow is "...the brightness of the night sky...as a result of light pollution."

Glare, on the other hand, can have several definitions. Together with the verb to dazzle or dazzle (like staring at someone), as a singular noun: "...someone is in the glow of advertising or an attentive public..." As an uncountable noun: "...a very bright light that is hard to look at, like B. the glare of car headlights." As a countable noun "A look is a look of anger, harshness, or hostility."

The end result, even for astronomy, is the glow, not the brightness of the sky, and vice versa. The glow, for you or me, may or may not cause a glow in the sky. You can say "a light shines in the night sky", but that's inappropriate English since there's no one to feel it.

Edited by GeorgeLiv, yesterday at 05:52.

Tony Flandes

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Agree, the brightness of the high sky implies an inevitable glare.

Not necessarily. For example, Central Park in New York has very high sky brightness and very moderate glare. Another situation that combines a high skylight and a low glow would be somewhere near a prison in a rural setting, quite a popular place to set up prisons for obvious reasons. As long as the prison itself is hidden behind a hill, there could be no glare, combined with a rather poor skylight.

Wilderness areas in or near cities are very common in the American West. The site of the old Riverside Telescope Manufacturers Convention had no glare and had a terrible glow from the western sky.

For me, low sky brightness means I can avoid glare, as low sky brightness means a low density area.

That depends on how low the sky brightness is and how accessible the attractive vantage points are. But you're right that anywhere you can get a good view of the Milky Way, it's probably not too hard to find a place with very little glare, especially if you have a car.

So for me Skyglow is the biggest problem because it can take hours to escape...

That is undeniable. It can be surprisingly difficult to find an open, glare-free area that is safe and legal to view. But once you find a place like that, it's probably pretty close to home. By contrast, it's a solid 2-hour drive from my home in Cambridge, MA to a location where light pollution is significantly weaker than the sky's natural brightness.

Edited by Tony Flanders, yesterday 06:12.

Tony Flandes

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image players Glow from the sky, no doubt.

On the right. Imaging is much less affected by glare than visual observation. It's fairly easy to prevent ambient light from entering the camera, but much more difficult to prevent it from entering the eyes.

jon isaacs

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My situation:

My backyard in San Diego is well protected from streetlights and other artificial lights, so glare is not an issue.

In the high desert, glare was not a problem until recently. The southern home was recently sold and the new owners installed motion-sensing lights along its driveway. Usually not a problem, but when the wind is 20 mph or more something triggers the lights and they come on for about 30 seconds.

I'll have to talk to them eventually, but my current plan is to park my truck next to the fence to block out the light.

The main concern is sky brightness, SQM readings vary from about 21.0 mpsas to 21.5 mpsas on the rare occasions when both the Imperial Valley and the San Diego Coastal District are cloudy. The coast is usually cloudy. Last night I measured 9:31 past midnight.

Jon

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Maximum height

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I'm lucky the faraway city flares aren't that big and are a bit far away, 5 and 50 miles. Because this is the high desert, it is generally dry and the brightness does not usually migrate to the usable part of the sky. At least not on good range nights. Added bonus, the sky glow is in places I don't keep an eye on anyway.
When I'm in my garden, glare is not a problem. I only have one neighbor and the general topography shields me quite well.
However, there is a third possibility. While the small town I live in doesn't produce a noticeable dome of brightness when approached from out of town, I think the addition of brighter and more lighting has degraded the Bortle number over the years. A new car wash, an auto parts store, upgraded lights at Wally World, a new gas station or two... I don't have an SQM, but over 15 years ago I could walk out of my house and see the Milky Way. easily, even before my eyes have adjusted. Now it has to be one of those special deep black sky nights to see it.

azur1961p

Hubble

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Neither. Right now, it's the Hunga Tonga above me that's taking my NELM.PETE down by two full magnitudes.

Jehujones

Apollo

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Does the brightness of the sky or the glow hurt more?

They are equally offensive to me for completely different reasons, so I can't pit them against each other.

Skyglow is stealing DSO from me in my backyard and it seems to be getting worse and worse.

Glare can ruin a nice session, especially if it's intermittent, say from a motion-activated light or a neighbor having a party or taking out the trash. Constant sources of glare can be compensated to some extent by installing blinds or blocking glare.

Sanbai

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And then, when you're trying to view comet C/2022 E3 from your (dense) suburban backyard, and the neighbors have their (empty) backyard lights on, even though it's a little chilly and not accessible to be outside, except to watch the comet. And then another neighbor's backyard light comes on, too, for an equally futile purpose. Also, there are some low clouds that reflect the light from the downtown area.

However, I located the comet with my binoculars. Then he quickly extended the little 80, pointed it roughly at a reference star, set the zenith, set the eyepiece, somehow pushed his elbow out of the reference, set the eye, focused... and there it was: magically pointing at! a perfectly centered comet!

Amazingly great and grand horrible prospects, but such are my prospects and my fortune. And I even tried my new comet filter, which *seems* to work (it's all I can say in such an environment, I need a miracle, not a filter...).

I still prefer no glow in the sky to no lamps. However, my previous views of the comet were in dark skies and near a streetlight illuminating two cabins in a remote cul-de-sac of a state park at full power in the middle of the night (at 5:30 am to be precise). . .

Editado por Sanbai, Hoy 12:34 am.