Eclipses

Lining Up At new moon the moon can block the sun. At full moon the earth can block the sun to the moon. This is called an eclipse. Solar eclipse, lunar eclipse

Kinds of Eclipses Solar Eclipse Lunar Eclipse Partial - crescent Sun Moon’s shadow on Earth Occurs at a new moon Partial - crescent Sun Total - all of Sun is blocked Annular - a ring of the Sun Lunar Eclipse Earth’s shadow on moon Occurs at a full moon Partial - moon partially dark Total - moon is dark red or copper-colored Earths atmosphere passes some light.

Elliptical Orbit The Moon has a synodic period of 29.53 days. the time from new moon to new moon. The Moon’s orbit is an ellipse. At the nearest, perigee, the distance is 363,000 km At the farthest, apogee, the distance is 406,000 km The period between perigees is 27.55 days. This is the anomalistic period.

Try It! Close one eye. Hold a coin out far enough to completely block the circle. Move out a little for an annular eclipse.

Annular Eclipse May 10, 1994, North Central United States Photograph by John Chumack

Orbital Inclination The Moon has an elliptical orbit tilted at 5.2° compared to the orbit of the Earth around the Sun. When the Moon crosses the Sun-Earth plane, it is at a node. The period between two ascending nodes is 27.21 days This is the draconic month.

Eclipse Seasons Conditions for a solar eclipse: New Moon (once every 29.5 days) Moon at a node (twice every 27.2 days) The circumstances happen about every 6 months. May 10, 1994: Annular eclipse in N. America Nov 3, 1994: Total eclipse in S. America Eclipse season lasts about one month.

Season Duration An eclipse season lasts about a month. Full moon for lunar eclipse New moon for solar eclipse Oct 8, 2014 Oct 23, 2014

Saros Cycle Convergence of cycles 223 synodic months is 6585.3 days So is 242 draconic months, and 239 anomalistic months Every 18 years, 10 or 11 days, and 8 hours the Earth, Moon and Sun are in the same position. These cycles were known since antiquity, and used to predict eclipses.

Total Solar Eclipse August 11, 1999: Szombately, Hungary Photographs by Michael Fortner

Viewing Eclipses Never look directly at the sun, even at a partial eclipse. It’s ok to look at lunar and true total eclipses. View sun through #14 welder’s glass or special mylar filters.

Great American Eclipse August 21, 2017 Total solar eclipse in a narrow band Partial solar eclipse outside band