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It took four attempts spanning three months, but it was worth it: finally, I sighted Yosemite’s mighty Half Dome from the summit of Contra Costa County’s Mt. Diablo.

Friend David Beckemeyer and I made the trip up last week, on February 5. This was two days after a good Bay Area rain, which cleared the atmosphere of dust. Half Dome is 130 some odd miles from Mt. Diablo, so the air has to be clean, clear, and cloud free.  Winter mornings are the best time to attempt the view, when seasonal humidity is low and before mid afternoon clouds start rolling in over the Yosemite Valley.

There are a few simple ways to get the bearing to Half Dome from Mt. Diablo. You can go up into the beacon lighthouse and use the compass rose there to find due east. Half Dome is 93 degrees off true north, almost due east of Mt. Diablo. If you’re using a magnetic compass, subtract about 15 degrees from its reading to account for magnetic declination in California. Either way you sight, a couple of degrees don’t make that much difference, as you will be scanning in the field of view anyway.  Look for Half Dome sitting on top of the ridge, where the ridge meets the sky. Good, bright binoculars (8×42 or 8×50) are required for a good view no matter how you sight. You can see Half Dome without optics, but you must know exactly where to look and the air must be very clear.  And even then it appears as the tiniest speck – so small that the eye can barely light on it for more than a second or two.

Yet a third way to sight Half Dome: Clifton Court forebay reservoir lies along the line from Mt. Diablo to Half Dome. The reservoir is the large rectangular body of water about 50 miles east. On an east-west line bisecting the reservoir, follow all the way up to the horizon. Half Dome is lurking near where the line meets the sky. David ginned up a map showing that line.

We stayed up top for about an hour, taking in the tremendous panoramic view, and showing Half Dome to the few passersby who wanted to know what we were up to. Mt. Diablo boasts one of the best so-called viewsheds in the world. The view of the snowcapped  Sierra Nevada, downtown San Francisco, the Farallon Islands (60 miles distant) to the west, is sight to behold.

It’s hard to describe how large Half Dome will appear in the binocolar or telescope view.  With my 8×50 binoculars, it took up maybe 1/20th of the field of view.  It’s not huge in that view, but it is easily discernible if you know what you’re looking for.  Its profile is unmistakable.

Here is the Half Dome webcam, situated in the Ahwahnee Meadow, which refeshes every half minute or so. During the winter, you have a front row seat to observe the hourly change in weather conditions that are common in the park. What a sight.