Mention “Hawaiian astronomy,” and most people think of Mauna Kea. The 13,803-foot (4,207 meters) peak on the Big Island hosts some of the largest and most prestigious telescopes in the world. But just an island away, on Maui, the summit of Haleakala has quietly been making a name for itself as a niche astronomical site, with viewing conditions nearly as good as its big sister.

Long known as a site for solar observing, Haleakala has more recently gained recognition for two asteroid-spotting survey telescopes, and it is a key site for the Department of Defense in tracking satellites and observing the near-space environment. The arrival of the Daniel K. Inouye Solar Telescope (DKIST), planned to begin operations in 2020, promises to raise Haleakala’s profile even further.

“It’s the best observatory site you’ve never heard of,” says astronomer Robert McLaren, interim director of the University of Hawaii Institute for Astronomy (IfA), which operates the high-tech “Science City” at Haleakala’s summit. As the tallest peak on Maui, the dormant volcano enjoys many of the same advantages of its sister site, he says. Those include its position as a mountaintop surrounded by ocean, which produces smooth airflow for outstanding seeing conditions; a mild climate with clear weather throughout the year; and a location near the equator that gives it a view of both the northern and southern skies.

Even though it’s 3,780 feet (1,152 m) lower than Mauna Kea, Haleakala is a big mountain in its own right. At 10,023 feet (3,055 m), its summit soars above mountaintops that house world-class observatories in the Canary Islands and many of those in Chile.