I saw this last night (using binoculars, full moon so it was extremely clear):
A black line or thin deep black and rigidly straight shadow crossing the Moon in the direction from SE to SSW. Amazing! I can't figure out what it could have been since the line advanced till it sectioned the Moon then slowly disappeared from the same direction.
In addition the section seemed to reduce in size by the time the line had crossed, even though the line remained straight and wasn't warped at all. Weird.
This was around 19h30-35 GMT.
Can anyone enlighten me?