After a visit to Mount Palomar's famous observatory, I enjoy introducing friends to the delights of the natural landscape right below the telescope's looming dome. In a kind of reverse pilgrimage, we follow the Observatory Trail downhill into shade-drenched ravines and sunny clearings, where bracken ferns spread like a lacy carpet. The trail traverses Cleveland National Forest land and has been declared a "National Recreation Trail" by the Forest Service, only one of four such trails in San Diego County.
The Observatory Trail roughly parallels the route of County Highway S-6 (Canfield Road, a.k.a. Highway to the Stars), so you have the option of hiking one-way, either uphill or downhill. It's best to start at the upper trailhead, just below Palomar Observatory's entrance gate, and have someone drive around to meet you at the trail's lower end inside Observatory Campground. A car-shuttle arrangement also works well -- there's only a two-mile stretch of road in between the trailheads.
Starting off from the upper trailhead, you pass through a thicket of dense chaparral and then enter a forest of pines, oaks, and incense cedars. About halfway down, the trail bends around a dark ravine, surely one of the nippiest spots in the county. Soon after, you reach a wooden platform overlooking Mendenhall Valley -- one of several large meadows tucked into Palomar's rolling flanks. Mendenhall Valley sheds water into the San Luis Rey River's West Fork. The water flows east to enter Lake Henshaw at Palomar Mountain's southeastern foot and ultimately makes its way toward the river's mouth at Oceanside.
Hiking the Observatory Trail is a fine experience during evening twilight. On warm late-spring or summer nights, you may spot green pinpricks of light dotting the trailside. Closer inspection reveals them to be the light-emitting organs of glowworms.