Atwood’s flash

Beneath the suitable geometry, a ray of daylight can slice throughout Hypatia’s in any other case shadowed crater ground. Such an occasion is probably going finest seen round a solar colongitude of 350° (or about 10° shy of First Quarter) — with the Solar about 13° excessive within the lunar sky as seen from Hypatia. In that case, the occasions are more likely to subsequent happen Feb. 27 at 1h26m UT and April 27 at 3h30m UT.

However on Jan. 16, 1986, Atwood noticed a phenomenon which can be a visible prelude to the well-known ray. He was utilizing his 8-inch Cave Astrola reflector to seek for the tiny craters named after the Apollo 11 astronauts when, at 1h13m UT, he noticed two rays of sunshine immediately “flash” into view in Hypatia. The view was akin to being in a darkish room when a door immediately opens a crack, permitting gentle to stream in. “The sunshine flashed on,” Atwood says, “and stayed on.”

On the time of Atwood’s sighting, the Moon was 5 and a half days after New, at colongitude 333° — effectively earlier than the anticipated ray ought to seem on the crater’s irregular ground. Certainly, Atwood’s good friend, Roy Parish (former coordinator of the Lunar Part of the Affiliation of Lunar and Planetary Observers), decided that Atwood’s flash befell when the Solar was about 3.5° under the lunar horizon, as seen from the middle of the Hypatia’s ground. Nonetheless, Parish notes that the Solar’s altitude would solely must be about 1° excessive to light up the hilltops north of the crater’s ground. (The crater has no central peak.)

Atwood’s sighting, then, simply often is the earliest recognized document of the primary glints of daylight slipping by the hole in Hypatia’s japanese wall on its approach to begin the ray. It’s attainable that atmospheric seeing might have produced distortions that magnified the obvious flash.