Also known as: Lunar X (Lunar craters Nonius K – Aliacensis – Werner crater)
Date/time: 2011.02.10 UT 16:10
Equipment: 76/900 Newtonian
Magnification and filter(s): 118x
Seeing: 7/10 Transparency: 3/5
Humidity: low
Wind: none
Location: Zákány, Hungary N46°14′ 59,2″ E16°57′ 15,3″
Observer: Bognár Tamás
Description
This is a famous „optical feature” on the Moon, which appears like the letter „X” when the terminator is at a suitable position. It is a fine example of how the combination of lighting and topography can combine to produce a pattern that repeats on each lunation, but only for a short time. The illusion of the „X” is created by sunlight falling on the rims/ridges between the craters La Caille, Blanchinus, and Purbach. The „X” is observable for about 4 hours around the lunar First Quarter.
This drawing is on the ASOD web page : http://www.asod.info/?p=5112
