Lunation length period "NASA - Eclipses and the Moon's Orbit" synodic month Draconic Month período sinódico Draconic Month synodic month Lunation length period "NASA - Eclipses and the Moon's Orbit" "NASA - Eclipses and the Moon's Orbit" Moon’s Orbit and the Synodic Month "NASA - Eclipses and the Moon's Orbit" Eclipses and the Moon's Orbit synodic month synodic month "NASA - Eclipses and the Moon's Orbit" siete horas synodic month "NASA - Eclipses and the Moon's Orbit" Moon's Orbit and the Synodic Month Draconic Month http://eclipse.gsfc.nasa.gov/SEhelp/moonorbit.html Eclipses and the Moon's Orbit