BOSTON (AP) — Advocates for keeping the night skies dark are gathering in one of the most light-polluted cities in the country: Boston.

The International Dark-Sky Association is holding its annual meeting starting Friday at a hotel in Boston's affluent Back Bay neighborhood. The Tucson, Arizona-based organization was founded in 1988, and its mission is to "protect the night skies for present and future generations."

Amanda Gormley, the organization's spokeswoman, says it picked Boston for the three-day gathering because some of its most dedicated and active chapters are based on the East Coast.

The densely populated region also happens to be where the country's worst light pollution is found.

A study published last year in the scientific journal Science Advances found that the Milky Way isn't visible for many residents living between Boston and Washington D.C. — a region that also includes New York City, Philadelphia and Baltimore.

Gormley noted the dark skies meeting comes on the heels of another, larger gathering in New England's largest city this week: the Greenbuild International Conference and Expo that opens Wednesday. U.S. astrophysicist Neil deGrasse Tyson and former President Bill Clinton are among the keynote speakers at that gathering, which bills itself as the world's largest conference on environmentally friendly construction.

Gormley says the dark skies conference will touch on similar themes as Greenbuild.

Speakers will focus on how policy and technology can be used to preserve the night skies, including ways advocates have convinced local policy-makers to adopt lighting technology that reduces light pollution, lowers energy consumption and saves communities money.

About 150 people are expected to attend, mostly advocates from the fields of science, planning and astronomy.

Among the local examples conference attendees will have a chance to visit as part of a guided tour is Salem, Massachusetts. The coastal city, where the infamous Colonial-era witch trials took place, recently installed LED streetlights and took other steps to become more environmentally friendly.