We got home late but not too late to still observe and image the Lunar X feature on the moon. The event peaked around 20:00 local but was still visible around 21:30 local. There was a thin haze and the sky was lit up by the moon.
We also observed visually using the 20cm “Starbuck” dobsonian. Very nice!

Unfortunately, the handyavi imaging program and the netbook could not communicate over the serial-usb adapter and we did not have remote control of the telescope, including the focusing.

Still we took a lot of .avi sequences and then screen captured one of them (shown above).


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.