Lunar month circular, the speed of Earth's progression around the Sun varies during the year. Thus, the angular rate is faster nearer periapsis and slower near apoapsis. The same is so for the Moon's orbit around the Earth. Because of these variations in angular rate, the actual time between lunations may vary from about 29.18 to about 29.93 days. The long-term average duration is days (29 d 12 h 44 min 2.8016 s). The synodic month is used to calculate eclipse cycles. It is customary to specify positions of celestial bodies with respect to the vernal equinox. Because of Earth's precession of
June 1991 lunar eclipse June 1991 lunar eclipse A penumbral lunar eclipse took place on Thursday, June 27, 1991, the second of four lunar eclipses in 1991. The moon entered the Earth's penumbra for about 3 hours, and was difficult to see. This lunar eclipse is the predecessor of the Solar eclipse of July 11, 1991. This eclipse is a member of Saros series 110. The previous event occurred on June 15, 1973. The next event was on July 7, 2009. A lunar eclipse will be preceded and followed by solar eclipses by 9 years and 5.5 days (a half saros). This lunar eclipse