Back then, the Naval Observatory was on 24th Street NW, in Foggy Bottom. It was an easy walk or carriage ride from the White House. On Aug. 22, 1863, Lincoln rode over, and Asaph Hall, the observatory’s astronomer, showed him the moon and the star Arcturus.
A few nights later, Hall heard a knock at the door. It was Lincoln, back with a question: Why had the moon been upside-down in the telescope’s eyepiece?
Hall explained that the observatory’s telescope worked differently from the surveying instruments and terrestrial telescopes Lincoln was accustomed to. Satisfied with the answer, Lincoln gave his thanks and left.
“He was an inquisitive guy,” Kirk said. “He didn’t just blow it off and not worry about it. He wanted to know.”