Eclipses Lining Up At new moon the moon

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

Orbital Inclination • The Moon has an 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

Season Duration • An eclipse season lasts about a month. – Full moon for lunar eclipse – New moon for solar eclipse Oct 8, 2014: Total Lunar eclipse Oct 23, 2014: Partial solar eclipse

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.

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

Total Lunar Eclipse • April 15, 2014: West Chicago, Illinois Photograph by Michael Fortner

Lunar 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

Saros Cycle • Convergence of cycles – 223 synodic months is 6585. 3 days – So is 242 draconic months, and 239 anomalistic months • Every 18 years, 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.

Track of Totality • Great American Eclipse of 2017 – Same saros cycle as 1999 Photographs by Michael Fortner

Upcoming Eclipse • If you missed 2017, next total eclipse in North America is April 8, 2024