Umbra ( ~ 1.4 x 106 km long)
Penumbra
At Moon's distance, the diameter of umbra ~ 9000 km, of penumbra ~ 16000 km
(Recall the diameter of the Moon, 3476 km )
The diameter of lunar umbra at the surface of the Earth is about 200 km, which varies quite a lot.
The shadow moves at about 1700 km/hr easterwards.
Line of nodes; eclipse seasons
Solar and lunar eclipse only occurs in the eclipse season, but in these seasons actual eclipse depends on more exact details of orbital motion.
Due to the precession of the Moon's orbital motion, the nodes move 19.4◦westwards per year with a period =18.6 year. Eclipse seasons come earlier than the previous year. An eclipse year is defined to be 346.6 days.
The Saros cycle:
223 lunar synodic months = 19 eclipse years
= 6585.3 days ( = 18 years 11.3 days, with 4 leap years included)
