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Every year, the International Dark-Sky Association (IDA) hosts International Dark Sky Week (IDSW). This is a weeklong event held during April that draws attention to the issue of light pollution, its harms and solutions. As it falls during Global Astronomy Month, IDSW is also a time to celebrate the night and the value of nighttime darkness. In 2023, IDSW takes place during the week of 15-22 April.
IDA is the world's foremost authority on light pollution and dark skies. Founded in Tucson, Arizona, in 1988, it aims to protect the night by educating the public about these issues. It also provides resources to those who want to improve outdoor lighting in their own communities.
"International Dark Sky Week is the time each year when we remind everyone about the value of protecting the night," said IDA's Director of Engagement, Bettymaya Foott. "It's fun and informative, and getting involved is easy."
The international community of dark-sky advocates celebrates the 20th anniversary of IDSW this year. A high school student named Jennifer Barlow of Midlothian, Virginia, originated the idea for an annual event in 2003. It began as "National Dark Sky Week" in the U.S., but the idea later spread to other countries. In the years since, organizations like the American Astronomical Society, the Astronomical League and Sky & Telescope magazine have endorsed it.
"Most of us have forgotten the legacy of the night sky as it seems to fade away behind the blanket of light pollution," Barlow told Sky & Telescope in 2006. "The universe is an important part of our history that should not be forgotten."
Image credit: Hoang M. Nguyen
IDA took over the annual promotion of IDSW in the past decade. It now consists of daily programming and events held throughout the week. In this way, the approach sustains attention to the issue. IDA also offers opportunities for those who want to become more involved in advocacy around dark-skies issues locally. The activities reinforce the idea that everyone can do something meaningful to reduce the impacts of light pollution.
The timing of the week matches the period when the lunar phase is waning after last quarter. That means the early evening hours are free of moonlight interference. Organizers encourage participants to go outside and see the night sky from wherever they live.
IDSW activities offer something for everyone. Because of the favorable Moon phase, it's a good time to make citizen-science measurements for the Globe At Night program. Having a look at the exterior lighting on one's home using IDA's self-assessment guide can reveal potential improvements. And anyone can use the platform of website, magazine and newspaper letters to the editor to express their thoughts.
Local groups increasingly host events during IDSW, including public lectures, night walks, star parties and more. IDA maintains an events calendar listing the details. Participants can also follow along on social media by using and following the hashtags #IDSW2023, #DiscovertheNight and #DarkSkyWeek.