A simple streetlight hack could protect astronomy from urban light pollution

a side-by-side comparison of two photos of the night sky; the one on the left is washed out by light pollution, while the one on the right is much darker
A comparison of images taken with and without the light-pollution-suppressing system. (Image credit: StealthTransit)

Light pollution is a growing threat to astronomy, but a new streetlamp technology could restore clear views of the night sky.

Light-emitting diodes (LEDs) consume only about 10% of the electricity required by traditional incandescent lights and last up to 25 times longer, so it's no surprise that they have become commonplace over the past two decades.

But there is a downside to LEDs: They're much brighter than old-fashioned energy-guzzling light bulbs. When an entire city gets fitted with energy-saving LED lamps, this bright light scatters through Earth's atmosphere and makes the sky glow with greater intensity.

As a result, many astronomical observatories, that in the past have been built in dark, remote locations, now see far fewer stars than they used to. In fact, the light pollution problem is worsening so fast that it offsets some of the improvements gained through advancements in telescope technology.

Related: Light pollution damaging views of space for majority of large observatories, survey finds

A study published earlier this year found that stars are disappearing from the sky at an average rate of 10% per year. This trend affects even the world's most remote observatories. Germany-based startup StealthTransit recently tested a solution to this growing issue.

"Unfortunately, this problem haunts almost all observatories today," Vlad Pashkovsky, StealthTransit's founder and CEO, told Space.com in an email. "Modern telescopes are highly sensitive and feel the impact of outdoor lighting of cities located at the distance of 50 or even 200 kilometers [30 to 120 miles]. This means that virtually every observatory on Earth either already needs, or will need in the future 10 years, protection from the light of large cities."

StealthTransit's solution relies on three components: A simple device that makes LED lights flicker at a very high frequency that is imperceptible to the human eye, a GPS receiver, and a specially designed shutter on the telescope's camera that can blink in sync with the LED lights. The GPS technology guides the telescope's shutter to open only during the fleeting moments when the LED lights are switched off. 

StealthTransit's system was installed on a 24-inch (60-centimeter) telescope during experiments in the Caucasus Mountains.  (Image credit: StealthTransit)

The experiments, conducted at an observatory in the Caucasus Mountains in Russia, showed that the technology, dubbed the DarkSkyProtector, could reduce unwanted sky glow in astronomical images by 94%. 

"We can say that the telescope was seeing almost a dark sky at this time," Pashkovsky said. "The important thing about our technology is that it makes all kinds of lights astronomy-friendly, including outdoor advertising and indoor lighting in apartments, offices and stores."

A 24-inch (60-centimeter) telescope featuring StealthTransit's DarkSkyProtector technology during experiments in the Caucasus Mountains. (Image credit: StealthTransit)

The technology could filter out lights from nearby towns and villages as well as those surrounding the observatory itself. 

It might sound impractical to refit an entire town with devices that allow lamps to blink, but Pashkovsky said that most existing LED lights can operate in the blinking mode and that new lamps designed specifically with sky protection in mind would be no costlier than existing LED technology. The most expensive element of the DarkSkyProtector system is the telescope shutter, which needs to be lightweight and agile enough to blink about 150 times per second. 

StealthTransit tested the prototype shutter on a 24-inch-wide (60 centimeters) telescope and hopes to make the technology available for larger telescopes. 

Although StealthTransit's technology is not yet ready for commercial use, Pashkovsky said, the firm hopes to have a product fit for the world's best telescopes in five to seven years.

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Tereza Pultarova
Senior Writer

Tereza is a London-based science and technology journalist, aspiring fiction writer and amateur gymnast. Originally from Prague, the Czech Republic, she spent the first seven years of her career working as a reporter, script-writer and presenter for various TV programmes of the Czech Public Service Television. She later took a career break to pursue further education and added a Master's in Science from the International Space University, France, to her Bachelor's in Journalism and Master's in Cultural Anthropology from Prague's Charles University. She worked as a reporter at the Engineering and Technology magazine, freelanced for a range of publications including Live Science, Space.com, Professional Engineering, Via Satellite and Space News and served as a maternity cover science editor at the European Space Agency.

  • Classical Motion
    How are you going to blink all the city leds at the same time?
  • billslugg
    They will have a GPS in each light fixture that will provide timing data so the lights are off during the times the telescope shutter is open. Current GPS chip available at $12 in quantity.
  • Classical Motion
    I believe that would be more difficult than thought.
  • billslugg
    They are not proposing a wide scale retrofit, this would be very expensive. The article says they will address only the lighting on observatory grounds or in the immediate vicinity.
  • Classical Motion
    If there was a demand, I'm sure they could stamp out a GPS switch for under a buck. But there more to it than that. There are many methods of switching, and now dimming and controlling leds. And even though the blink is too fast to see. There will still be a dimming when the switch is deployed. Most won't be effected, but others will be. And the switch will cause problems for some control methods.

    The installation time and cost will far out weigh the GPS cost.

    If one is sure they want this solution......then put the GPS right in the led at manufacture. Then it might be worth it. Or at least commonly applicable.
  • ericptak
    I have concerns on how the blinking lights would affect people with epilepsy. Our son has it, and blinking lights trigger seizures.
  • Stuart21
    Classical Motion said:
    I believe that would be more difficult than thought.
    The main problem is poorly mounted lights - such that light is emitted above the horizontal good shades & good mounting (w help of a spirit level - prob solved -
  • Astrofriend
    I wrote about this idea on my homepage 8 years ago:

    To controll a bigger area it will cost a lot of money to install.

  • ProfessionalDisaster
    I have concerns about the flickering as well. I can only see some older LEDs flickering, but many more can trigger migraines for me and others even though the blink rate may be consciously "imperceptible to the eye". I get the same thing from flickering fluorescent lighting, and even some of the "flame" bulbs. Night driving is bad enough with the LED headlight issue.
  • kb-
    A fix to lights 200 km all around observatories, that would not help the wildlife and common people with the light pollution issue🤔 Good luck with that!
    It's best to reduce hours and add reflectors