Mike L.
Yelp
MacDonald Observatory is, bar none, the absolute best place for stateside assisted star-viewing. The extraordinarily friendly staff routinely hosts Star Parties, and gives a brief late-dusk primer on that night's best viewing. It's so good, it was rated #1 in the world by Lonely Planet.
Located 6,500 feet up in the Davis Mountains (near Davis Mountain State Park - see other reviews for that) of West Texas, the observatory is blessed by some of the clearest skies in North America. Because of this, nighttime viewing of major astronomical bodies and events is already far above average. Add to that a dedicated staff using pro-line telescopes (better than you can buy in most stores) and offering take-as-long-as-you-like views of some of the best objects in space, and you've got an unbeatable experience.
Crowds vary, but it's said to range from 50-200 people per night. Have patience, though, and be prepared to be humbled by the sheer infinity of space.
Price: $10 (!!! WOW !!!)
What to bring: Warm clothes / layers / blanket (it's at 6,500 feet, and even if it's a warm day, it's guaranteed to be a nippy night); binoculars/your own basic telescope (the dedicated scopes are all pointed at something, and there are lines, so you'll want to have some filler); a red-LED (to find your way around); your joyous curiosity.
PRO: Cheap, organized, uber-friendly, unique
CON: Chilly, semi-remote
The observatory also hosts special dinners / viewings on their larger scopes (up to the 107), twilight shows ($5), and moon viewings.
The observatory tour is interesting, but is more suited to amateur astronomy buffs. The star part is suited to everyone.
Nearby/See Also: Davis Mountains State Park, Scenic Drives, Balmorhea Hot Springs