The Lunar X, also known as the Purbach or Werner Cross, appears at First Quarter near the terminator between the craters La Caille, Purbach, and Blanchinus. It sits 25° south of the Moon’s equator and dead-center left to right. When the Lunar X is visible, sunrise is occurring over this region. Ohio amateur astronomer Dana Thompson captured this image of the Lunar X January 25, 2007, at 7:33 p.m. EST.
Dana Thompson
In the October issue of Astronomy, I wrote about 12 easy-to-observe lunar targets. One, the Lunar X, is visible only for short periods of time. Astronomy magazine Contributing Editor Alister Ling authored software that gives the times the Lunar X feature will be visible, as well as the locations. He graciously provided this table, which is specific to North America.
