If you’ll be in San Francisco between 8 p.m. and 9 p.m. on Saturday, Oct. 20, be sure to have a candle handy. Green group Lights Out San Francisco is encouraging residents to turn off all unnecessary lights during that hour to raise awareness of energy use. Nate Tyler, a former Google spokesperson who is spearheading the campaign, was inspired by a trip to Sydney during its annual light-extinguishing Earth Hour in March; he has printed up “Good Things Happen in the Dark” T-shirts and plans to give away 110,000 energy-efficient bulbs on the day of darkness. Just imagine: Without light pollution from homes, car-lot floodlights, movie marquees, and high-rises, San Franciscans will be able to take out their telescopes and have a nice clear view of the fog.