How to find a darker sky

One of the most dramatic improvements you can make in the quality of your visual observing is by getting to a darker sky. Most of us live in or near big cities, or at least larger towns. Getting away from all those lights will allow our eyes, binoculars, and telescopes to see more in the night sky. Today, being mobile is more important than ever. Even imaging and electronic assisted astronomy benefit from darker skies, despite the ability to counter light pollution to an extent through technology. Some amateur astronomers say that the best filter for your telescope is the "car filter." Get in a car and drive somewhere darker.

(Above: The sky at Arizona Sky Village. Photo by Astronomerica)

If you are new to astronomy and you are lucky enough to live in a reasonably dark sky without neighbors who try to banish the evil darkness with all-night lights, you may be able to do most if not all of your observing at home. But most of us aren't so lucky, and home observing must contend not only with pervasive sky glow but neighbors' lights, streetlights, parking lot lights, headlights, building lights, etc. I only observe the Moon, bright planets, and occasional double stars from home. Everything else means driving somewhere else to get better views.

Contact a local astronomy club

The best way to find observing sites that are reasonably dark, have little or no glare from local lights, are safe, and have decent horizons is to locate and contact your local astronomy club. Chances are that someone has already done the hard work of finding suitable locations and negotiating with the powers that be for the use of that land at night for observing. I am lucky to belong to the Northern Virginia Astronomy Club, one of the largest amateur astronomy clubs in the United States. We have numerous sites from suburban to dark sky, depending on how far you are willing to drive.

Being a member of a club usually gets you access to sites that the general public may not be allowed in at night. It will also give you information about members' favorite sites that may not be official club sites, but are still viable places to observe.

Do your own research

If you don't have a nearby club, you can do your own research, or ask on the various fora such as Cloudy Nights, Stargazer's Lounge (for the U.K.), The Sky Searchers, or various Discord servers what others might recommend. This also works if you are traveling and want to know where a good place to observe might be. For your own safety, never tell anyone except relatives and trusted friends where you are going to observe, but make sure someone knows where you are.

The most accurate light pollution map is the one developed and maintained by David Lorenz, called Light Pollution Atlas. The most recent data is from 2023 and the satellite data and methods he uses to determine sky brightness seem to be more accurate than other light pollution maps. If you click on a point, it will tell you the year of the data, the latitude and longitude, and the sky brightness measured in magnitudes per square arcsecond, close to what you would get if you used a sky quality meter (SQM) to measure the sky (shown above), as well as a ratio of artificial/natural brightness. These are all approximations in the map, and tend to still be overly optimistic especially while we are near solar maximum, but give you plenty of information to see how skies compare relative to each other.

Left: It's a long drive to a dark sky from the Northeastern U.S. megalopolis. The dark blue near the top is the area around Cherry Springs State Park in north-central Pennsylvania, a favorite observing spot for those in the region. The other blue area in the lower left is in the mountains of West Virginia, home of the Almost Heaven Star Party.

(David Lorenz, Light Pollution Atlas)

You may hear people say that they live in an orange zone, or in Bortle 5, for example. The color refers to the color scale of more basic maps, which ranges from white (brightest) to black (darkest). The Bortle Scale was invented by amateur astronomer, comet observer, and contributor to Sky & Telescope magazine John Bortle, and is a scale to measure the brightness of the sky in a particular place and time based on what can be seen in the sky. More people will refer to their site using the Bortle Scale than with an SQM reading, so it's good to know what both mean. Scroll to the bottom of this page to see a rough comparison chart. (Your browser may warn you the site is not secure. Proceed only if you trust those nefarious amateur astronomers!) 

Lorenz's atlas appropriately does not use the Bortle Scale because it is dependent upon observations on a specific night by a specific individual, assuming they didn't just read it off a map. However, if someone who has a reasonable amount of observing experience tells you he or she estimated that a site was Bortle 2, you can be pretty certain it's nice and dark and you will not be disappointed observing there on a good night. But most people don't actually bother trying to make Bortle Scale observations. I prefer looking at the Atlas or just staying away from population centers.

Here is the color scale from David Lorenz's atlas, calibrated to the brightness readings:

Although the SQM readings are more precise, I personally find it much more difficult to remember how good a sky is based on the SQM number. For example, my usual semi-dark site is listed at 21.01 (greenish-brown). The site I camp at is 21.28 (green). My home is a sickening 18.42 (red bordering on light gray). 

I figure anything around 21.0 and higher is usable for deep sky observing and I can get some decent views that are worth driving an hour or so. Anything about 21.7 and higher is going to be very good to excellent, and there are only two big areas in the eastern United States like this—in the mountains of West Virginia and in north-central Pennsylvania—that have suitable observing places, unless you own private property in the Adirondack Mountains and have cleared some trees. But these are difficult number ranges to remember, so I get why people use the color scale or Bortle rating. Looking at the map, it's much easier to see where you need to head for dark skies because of the color scale.

Other considerations

A dark sky is not the only criterion. There is the weather, dust, and wildfire smoke. Also avoid hours where the Moon is up. You need a good horizon. As noted, the Adirondack Mountains in upstate New York get as dark as 21.91 (see above), if you believe the map readings, but good luck finding some open sky. 

You want to avoid parks that close at dusk (almost all local and state ones) unless you like talking to the police, stay off private property without the owner's permission, and avoid dangerous places. An airport runway might seem like a great place until a Cessna flies out of the darkness and tries to land on your head. (Cessna 152 by Ramon FVelasquez, CC BY-SA 3.0, via Wikimedia Commons, with edits)

You also need to be away from nearby lights, which is a much more difficult endeavor than it might seem at first, as many people absolutely LOVE all-night "security" lights. I've always thought this was odd, because no one is out there in the middle of the night to see prowlers moving around. Well, except for astronomers, who unfortunately won't be there to scare off the prowlers because YOUR LIGHTS ARE TOO ANNOYING! I will leave you with one of my "poems" from the Redneck Patio (see link at right):

Criminal

Porch lights

Garage lights

Whitewash the suburban wasteland

And kill the sky

As I draw chalk emojis

On the driveways,

Unseen.

🙉🙈🙊 

Build your own Redneck Observatory

Redneck /rĕd′nĕk″/ (adj.) - Where there’s a will—and duct tape, a few bungee cords, some plywood, and maybe a few wood screws—there’s a way.

The two enemies of a dark sky are sky glow (a bright glow in the sky resulting from myriad city, town, and industrial lighting) and glare (nearby lights that shine in your eyes and create light trespass). You can’t do much about sky glow other than move somewhere where it’s darker, but you do have some options to deal with glare and light trespass.

Dealing with local lights, your options are:

1. Move somewhere else. Not feasible or even advisable for most people, at least in the short term.

2. Find a better place to observe. Whether it’s down the street or somewhere you need to drive to, it’s usually the best option, and you can often improve both the sky glow and glare situation. But we don’t always want to cart our gear beyond our home environs, and some nights it may only be clear for a short time and we want to take advantage of that right at home. Plus there’s the convenience and safety of being at home.

3. Talk to neighbors about shutting their lights off at night, shielding them, or putting motion sensor lights in. If you have only a couple of offending lights, this might work in the short term, but even cooperative and friendly neighbors will forget or want them on at times. My neighbors clearly believe all-night lights keep crime away and make them feel safe from the dark. I won’t get into the issues with that philosophy, but they have a right to think the way they do and I’m not likely going to change that.

You can also offer to show them stuff in your telescope and approach the lighting issue that way. Recently, I was at a cabin in the mountains, and my brother and I set up our telescopes outside our cabin. We set up before it got dark and it attracted the attention of our neighbors in the other cabins. By the time we were done showing them some objects and chatting about astronomy, we had no lights to worry about the rest of the night.

4. Accept the sky glow and block out the local lights. That’s what I’m talking about here.

At my house, the backyard is mostly blocked by trees and other houses. Therefore, I have to observe in the front yard. All of the neighbors up and down the street have all-night garage and porch lights, usually ten blazing away, none of which are shielded, and only one of which is on a motion sensor. In addition, I have headlights from a busy intersection shining directly at me as cars wait at the red light.

I took control of the situation and built what I call my “Redneck Observatory."

My observatory consists of found objects like my garbage and recycling cans, so I guess I could also call it my “Dada Observatory.” I have a car parked on one side of the driveway, I use frames from the packing of a bathroom sink we had installed, a PVC pipe holder for a target frame I built, some cheap moving blankets, some plastic spring clamps, and a few bungee cords.

The plan was to use stuff I already had sitting around nearby that would be easy to throw together to block out the lights. The car is usually parked there, so I just put a 4x4 piece of wood, left over from stacking flooring, along the edge of the roof with a short extension to hold a small moving blanket in place. The blanket is clamped to the end of an upright frame consisting of the aforementioned bathroom sink packing frame with a height extension made of furring strips (my favorite cheap wood) and old baseboard from the flooring job.

A packing frame leans against the garbage can and is bungeed to it to keep it from falling in the wind. The other packing frame (never throw stuff out that you might be able to use) leans against the recycling can and is likewise bungeed. A big moving blanket is thrown over both frames and clamped in place with spring clamps. The third wall, on the right, is my old PVC target stand with a frame made of furring strips and old baseboard, again with a moving blanket thrown over it and clamped in place.

It takes me 20 minutes to set up and break down if I take my time. Not my casual or optimistic estimate, I actually timed it. If I observe for an hour or more it's worth it to me. Rarely do I observe for a shorter time.

So before you give up, look around the house and see what you have. Maybe you can build your own Redneck Observatory.

 

Light pollution and the future of amateur astronomy

Photo by VillageHero (CC)

A thread on the Cloudy Nights forum got me thinking about light pollution and the future of amateur astronomy, especially the visual astronomy that I love so much. I can only say for certain that amateur astronomy, for those whom circumstances allow, will still be an enjoyable hobby in the future in some form or another.

Based on trends I'm seeing now from my limited point of view, cheap Electronically Assisted Astronomy (EAA), or some semblance of it, will likely be the mainstream portal for new amateur astronomers or casual hobbyists until the next big thing comes along. We're almost there already. EAA is the use of a camera in lieu of an eyepiece at the telescope to capture and view images in near real time. It has recently become more affordable with the introduction of the Seestar S50 Smart Telescope, which is often paired with a tablet on a tripod for viewing its images. While still hindered by light pollution, these telescopes can cut through much of it, making for satisfying imaging even in light polluted areas.

People want to create something to share on social media, not just look at stuff. Who creates astro images and doesn't share them online? Here I am sharing material on visual observing because I can't share the actual views themselves, other than describing them in words or sketches. Social validation is huge in our society, probably always has been, and I don't see that changing.

I think most astro-imaging will be done from the comfort of home using data obtained in the backyard, from remote telescopes, and from data shared online (like Hubble data). Why drive way out, freeze in the cold, set up equipment, etc. when it will no longer be necessary? 

Will light pollution still be an issue for amateur astronomers? I think it will likely only be a pressing issue for a shrinking group of visual astronomers. Imagers, who used to be the biggest proponents of keeping the sky and observing field dark, now can obtain and process fantastic images from horribly light polluted locations, like this one from someone's backyard in Washington, DC. They can reject frames ruined by light, satellites, planes, clouds, etc. Sure, dark skies are better, but are no longer essential to create great deep-sky images. Visual observers have no such recourse.

At our public and club-only star parties, imagers are now the ones with bright unshielded screens, along with those with EAA setups, because dark adaptation no longer matters to them. At the latest public event, a young girl asked me, "Why do you ban white lights and pass out red filter material for our phones when you all have your bright white screens on?" I couldn't answer her.

In the foreseeable future, I think a few visual observers will be the only amateur astronomers with the self-interest to fight light pollution, and it may be mainly wildlife enthusiasts that take up the torch (see what I did there). I think most visual observers will just drive (or move) somewhere darker, or observe the bright planets, the Moon, the Sun, and double stars at or closer to home. That's what I do now.