A penumbral lunar eclipse took place on Tuesday, December 20, 1983, the second of two lunar eclipses in 1983. At the maximum eclipse, 89% of the Moon's disk was partially shaded by the Earth, which caused a slight shadow gradient across its disc; this subtle effect may have been visible to careful observers. No part of the Moon was in complete shadow. The eclipse lasted 4 hours and 2 minutes overall.[1]