Under the right geometry, a ray of sunlight can slice across Hypatia’s otherwise shadowed crater floor. Such an event is likely best seen around a solar colongitude of 350° (or about 10° shy of First Quarter) — with the Sun about 13° high in the lunar sky as seen from Hypatia. In that case, the events are likely to next occur Feb. 27 at 1h26m UT and April 27 at 3h30m UT.
But on Jan. 16, 1986, Atwood saw a phenomenon which may be a visual prelude to the well-known ray. He was using his 8-inch Cave Astrola reflector to search for the tiny craters named after the Apollo 11 astronauts when, at 1h13m UT, he saw two rays of light suddenly “flash” into view in Hypatia. The view was akin to being in a dark room when a door suddenly opens a crack, allowing light to stream in. “The light flashed on,” Atwood says, “and stayed on.”
At the time of Atwood’s sighting, the Moon was five and a half days after New, at colongitude 333° — well before the expected ray should appear on the crater’s irregular floor. Indeed, Atwood’s friend, Roy Parish (former coordinator of the Lunar Section of the Association of Lunar and Planetary Observers), determined that Atwood’s flash took place when the Sun was about 3.5° below the lunar horizon, as seen from the center of the Hypatia’s floor. However, Parish notes that the Sun’s altitude would only have to be about 1° high to illuminate the hilltops north of the crater’s floor. (The crater has no central peak.)
Atwood’s sighting, then, just may be the earliest known record of the first glints of sunlight slipping through the gap in Hypatia’s eastern wall on its way to start the ray. It’s possible that atmospheric seeing may have produced distortions that magnified the apparent flash.
