The skies above Borrego are among the darkest in Southern California — dark enough that on a moonless winter night you can see the Milky Way casting a faint shadow on bare ground. Astronomy clubs in San Diego make pilgrimages here with telescopes, and the local Borrego Springs Performing Arts Center occasionally runs public star parties.
You don't need a tour to enjoy it. Drive ten minutes north on Henderson Canyon Road or east on Borrego Springs Road, find a turnout, kill the headlights, and give your eyes fifteen minutes to adjust. New moon weekends are best; winter offers Orion and the Milky Way's brightest section.