We have some of the worst light pollution in the contiguous 48 states… but also some of the best skies in the western hemisphere! California’s diverse topography and distant spread of cities, along with steady pacific air provide wonderful dark sky access, as long as you distance yourself from the abundantly bright and ever-growing urban areas. Dark skies, as you can see in the light pollution map below, still exist in the remote high elevation areas, as well as some of the coastal regions which can potentially yield extraordinary seeing conditions of less than 1 arcsecond of resolution. That’s good news for astro-imagers and high-power observers with large scopes.
But look closer.. for such a large population, and under terribly light polluted skies, we’re just a couple hours or less from remarkably dark and steady skies. That’s a good news spin on the situation, I think. It’s one thing to trek out to the middle of Nevada or New Mexico for the purpose of astronomy, but something else to cruise over to magnitude 7 skies a couple of hours from the SF or LA area. That kind of accessibility to such a large population gives more people a chance to appreciate astronomy and the importance of suppressing light pollution. Plus, many urban-dwellers are absolutely floored when they see the Milky Way, or their own shadow cast by Jupiter. That fresh awe-factor can make someone moon-eyed for California’s dark skies under moonless nights.
As Tony Hallas has indicated in the April 2012 issue of Astronomy, the Modoc Plateau in northeastern California still has some of the most spectacular skies anywhere. Also, you can’t go wrong with Trinity, Shasta, Siskiyou, Lassen, and Mendocino counties, if you don’t mind the drive. Monterey county has some sleeper locations that are surprisingly good, especially around the Ventana Wilderness and Santa Lucia mountain range. Lake San Antonio is not far from there, and offers some recreational variety for those planning to guise their stargazing trip as a family event on the lakefront.
Of course, there’s still the high Sierra and remote high desert areas like Mojave and Joshua tree – both great places for star gazing and imaging, with an extra dash of unpredictable weather to keep things exciting.
Light pollution map data provided by The World Atlas of the Artificial Night Sky Brightness. I drew in the CA state border in red.