Heading to the mountains and looking to the stars are two cherished summer pastimes. You can combine both by flying to any of these four mountain observatories, which are among the world's finest, or an historic fifth one in the hills of Wisconsin. Once you've arrived, you can combine stargazing and learning about the heavens in observatory tours with more customary summertime activities like hiking and beach-going.

Kona, Hawaii

As if you need another excuse to fly to Hawaii, add one more: the Mauna Kea Observatories on the volcanic “Big Island" of Hawaii. Astronomers adore Mauna Kea's thin, dry, clean air, continually purified by trade winds, which lets them peer easily into space from the world's largest array of telescopes atop the world's tallest mountain. Yes, the tallest (13,802 feet) — but only if you start from the base of the mountain, which is four miles below sea level. It's about a 1 ½ hour drive from the resorts of Kona (or Hilo) to the 9,200 foot elevation visitor center, where you can view the sun through a solar telescope or the stars through a night scope. You can also attend a special program on most Saturday nights.

Santiago, Chile

Several of the world's finest observatories are clustered on the cloudless, high-altitude plateau of the Atacama (the driest desert in the world), making northern Chile the favorite destination of “astrotourists" from around the globe. The top two for visitors are the Paranal Observatory, with its aptly named Very Large Telescope (VLT), and the ALMA Observatory, the world's largest and priciest ($1.4 billion) astronomical project, with a telescope more powerful than the Hubble. You can venture out to tour them after flying into Santiago where you can take in: the nightlife, the culture of nearby Valparaiso, the beauty of national parks in the Andes, and the beaches and wine regions of central Chile.

Tucson, Arizona

While golfers brave triple-digit temperatures on Tucson summer days, visitors who brave the twisty 31 mile drive from Tucson to Mt. Lemmon arrive in sweater weather at the 9,157 foot summit. The University of Arizona's Mt. Lemmon SkyCenter is both literally and figuratively cool, as you may spot a meteor or satellite through the Southwest's largest public telescope during the nightly, five-hour stargazing program ($65/adults, $40/youth, dinner included). Summer or fall is the best time to go. Kitt Peak National Observatory, atop a 6,877-foot mountain, is also a 90 minute drive from Tucson, featuring a visitor center and daily 3 ½ hour guided tours of its massive telescopes ($9.75/adults, $3.25/youth).

Tenerife, Canary Islands

The Canary Islands, an autonomous territory of Spain off the Moroccan coast, is a favorite getaway spot for Europeans and is cherished for its beaches, volcanoes and mild climate. On the island of Tenerife, Teide is the shared name of: the national park (a UNESCO World Heritage Site), the tallest mountain (12,198 feet), and the sprawling observatory situated partway up the volcanic mountain. On it you'll find a visitor center and an array of telescopes, which will give you a good look at the galaxy during guided English-language stargazing telescope tours every Friday ($34/adult, $27/youth, by reservation). A second major observatory in the Canaries, Roque de los Muchachos on the island of Las Palmas, offers daytime guided visits (70-90 minutes) by arrangement.

Williams Bay, Wisconsin

Only the most serious astronomy buff would make a special trip to Williams Bay (pop. 2,600, elev. 1,050 feet), but it makes for a pleasant small-town diversion on a trip to Chicago, Milwaukee or Madison, which are all within a 90-minute drive. Why? Because oddly enough, the village on Geneva Lake is where you'll find Yerkes Observatory, regarded as the birthplace of modern astrophysics. Research at the University of Chicago-operated facility has continued since it opened in 1897, but visitors can stop by any day except Sunday for a 45 minute daytime tour ($8-$10), or most evenings for a telescope stargazing program ($37.50 by reservation). While in town, you can hike through the Kishwauketoe Nature Conservancy or visit Williams Bay Beach.

If you go

Visit united.com or use the United app to plan your stargazing adventure.