Not All Dark Skies Are Created Equal

Not All Dark Skies Are Created Equal
By Shannon Kalahan.

I don’t remember seeing the Milky Way when I was young. It was a thing I’d heard of, but I lumped it into the category of a dragon or a unicorn. In my mind, the Milky Way was just an abstract concept, not something that existed within the realm of my existence. Afterall, I grew up in the suburbs, somewhere between Boston and New York, where night skies are slowly dying.

A few years ago, well after I’d started on my landscape photography journey, I decided to learn astrophotography. The technical aspects of capturing stars seemed simple enough. I had my aperture settings (f/2.8 on a cheap, wide angle lens), I had my time values and an idea of ISO range, and I had my tripod. Add in a compass app, a Milky Way app, and a headlamp, and I was ready. All I needed to do was practice, right?

Wrong.

The first and ever-present struggle in my home state of Connecticut is finding an accessible, open space facing south. We have a lot of trees and almost no elevation. Overwhelmingly, the unimpeded views in my area involve water–a pond, lake, or an hour drive to the ocean. The alternative is a long drive.

The second, and arguably bigger challenge, is finding dark skies. The bortle scale is a way to rate dark skies, with “one” being excellent dark skies and “nine” being what you expect to find over an inner city, like say, New York. Oh, and did I mention Manhattan is directly south of me? The darkest skies in my local area are rated either a four or five on the bortle scale, and none of them have International Dark Sky Association designation.

www.go-astronomy.com/dark-sky-parks-stargazing-state

Light pollution has become a huge problem in many parts of the world, mine included. Most flora and fauna have evolved to follow a natural circadian rhythm. According to the National Institute of General Medical Science, circadian rhythms are: physical, mental, and behavioral changes that follow a 24-hour cycle. These natural processes respond primarily to light and dark and affect most living things, including animals, plants, and microbes.

Studies have found that filling the night sky with excess light is detrimental in so many ways, including increased risk for anxiety, obesity and cancer; ecosystem disruption, biodiversity and migratory issues in animals; wasted money and fossil fuel in the form of wasted energy; and a loss of our night sky heritage. For those reasons, the IDA has worked hard to educate people and encourage smarter lighting use and design. After thirty-four years, as of January 2022, there are almost 200 parks, reserves, sanctuaries and communities around the world that have obtained an International Dark Sky Place designation.

International Dark Sky Places
The International Dark Sky Places program certifies communities, parks, and protected areas around the world that preserve and protect dark sites through responsible lighting policies and public…

So what did that mean for me, and my pursuit of astrophotography? Well, the closest IDS recognized space, with a bortle rating of two, is six hours away. In other words, I either needed to learn to compensate for the light pollution, or learn to like long drives. Ultimately, I did both.

In order to create images in the New England / New York area, I typically set my ISO somewhere between 1200 - 3200. Because there is so much ambient light, higher ISOs will overexpose the scene. I typically shoot between 10-13 seconds, depending on what focal length I’m using—the 500 rule can give you a starting point. I also create multiple exposures in order to cover the various lighting scenarios within the scene. For example, I may take a foreground shot at a lower ISO for several minutes if I didn’t capture it during blue hour (both techniques reduce foreground noise), and an underexposed image for things within the frame that have light pollution shining directly on it. I’ll also take a series of the sky to later blend for reduced noise, as I do not have a star-tracker. The final image almost always involves compositing multiple exposures to simulate the scene as I experienced it. I’ll also go through and clone out random glare points along a horizon if the image will benefit from such clean up. Light pollution, by its very nature, adds extra steps to my editing workflow that aren’t needed in dark sky areas.

Another compensation technique I’ve come up with is to block some of the New England sky glow by using creative compositions. A series of trees, a gap in a ridge that the Milky Way lines up with, that sort of thing.

Now comes the travel part. I live in an area with a bortle class six sky. The absolute closest sky in which I can photograph the core of the Milky Way without the core being washed out is about 1.5 hours away, a bortle class four. Even then, I can’t see details of the core with my naked eyes. At best, it looks like a light-ish smudge arcing through the sky. At worst, I have to point the camera in the right general direction and do test shots until I find a composition that works. So, while I can and do make drives around New England for astrophotography, nothing I’ve seen here compares to dark sky areas like Death Valley National Park or Arches National Park in the American Southwest, or along Iceland’s southern coast. All of those skies are bortle class two, and have a significant distance between them and major light pollution centers to the south. When I have been fortunate enough to photograph those skies, my ISO settings have always been 3200 and above. The higher sensitivity was needed for those darker scenes. Although I still took multiple exposures for foreground and noise reduction, there was no need to spend additional time compensating for spots of light pollution within the scene or cloning random light blobs off a horizon.

During my most recent trip out west, I spent a few nights under the stars. I remember feeling excitement, joy and peace. The Milky Way was no longer an abstract, a mythical unicorn never to be seen. It was there, right in front of me, stretching its way from horizon to horizon. Watching the constellations and the milky way sparkle and glow, with just my naked eyes, felt right. Unfortunately, that means that all of my astrophotography attempts around New England since then have landed somewhere between mediocre and inadequate. It’s shocking what a difference a truly dark sky can make in the quality of your images, the amount of work you need to put in, and the caliber of your overall experience. And even worse, driving all night and coming away with a crap photo takes a toll on my motivation—who wants to put in hours and hours of their time just to come up short because of things beyond their control?

Spoiler alert: not me! But what we want in life is rarely what we get.

Ansel Adams is quoted as saying, “A good photograph is knowing where to stand.” In order to take the best Milky Way images, I’ve come to the conclusion that I do need to stand in the right location. I need reduced light pollution, and the right weather, at the right time of year, working around moonrise and set. However, it takes a lot of failed images to become proficient in astrophotography, and I’m honest enough with myself to admit I still have a ways to go. So, until we reduce the amount of light pollution in New England, or I travel to another dark sky location, I’ll continue to both support the IDA’s mission and practice photography techniques locally. I know the images I take will never make it to my portfolio. I know I’ll feel disappointed and frustrated with how bright the frames are. But I also know that practice makes progress. After all, Ansel also said, “The single most important component of a camera is the twelve inches behind it.” So, after all these years, I’ve managed to make my way full circle from the start of my astrophotography journey to now. I’ve still got my settings, my tripod, and my headlamp. I need to keep putting in the work.

For more peer reviewed articles than you’ll ever want about the effects of light pollution, click here: www.zotero.org

Finally, a few tips for better astrophotography, no matter what type of sky you find yourself in:

  1. Understand how your camera settings work so you can adjust on the fly.
  2. The 500 rule (500 / focal length of your lens) is just a starting point. Always check your test image for star drag. If they’re not round stars, but rather oval or elongated, then you’ll need to shorten your time value.
  3. If you intend to take multiple frames and blend them, turn off your auto white balance. Nothing worse than spending a few hours under the stars only to find out you can’t blend the images you captured.
  4. A red headlamp is a worthwhile investment. It saves your eyes, and helps reduce unnecessary light pollution. This is particularly important if you’re not shooting alone.
  5. Be respectful. If there are multiple people at a location, please communicate before you start flashing lights everywhere. Ask if they're running a long exposure. Ask if they want the foreground light painted. Ask if they’re done before you get in your car and drive off, headlights blazing