Fort Davis is 30 miles north of Marfa on Route 67.
The McDonald Observatory is atop Mt. Locke. By day, visitors can tour the telescopes and the planetarium ($8 adult, $7 children), which are owned by the University of Texas. The real attraction, though, are the Star Parties ($10 adult, $8 children) after dusk on Tuesday, Friday and Saturday. (Nov-Mar: 7:30PM, Apr-Aug: 9:30PM, Sep-Oct: 9PM) Two of the observatory's more powerful telescopes - as well as several smaller ones - are set up outside for visitors to catch a startlingly clear glimpse of star clusters, distant galaxies and even a member or two of this solar system. The altitude and the remote location ensures that light pollution is kept to a minimum, and enthusiastic guides are on hand to explain exactly what the scopes are showing. Bring a warm jacket regardless of the season, as the temperature drops rather steeply at night.