Mercury's transit in front of the sun, as seen from SLO
Mercury appeared as a black speck as it transited the sun Monday morning in a view from the Bowen Celestial Observatory at Cuesta College.
Although Mercury passes between the sun and Earth every 116 days, its orbit is tilted so the planet will only move across the face of the sun an average of once every 24 “pass betweens,” or about 13 times a century. The next transit of Mercury will occur Nov. 11, 2019.
The viewing required a special narrow wavelength-band filter mounted on a 14-inch telescope, which blocked 99.99 percent of sunlight.