1. Eclipses

2. 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

3. 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.

4. 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.

5. Kinds of Eclipses  Solar Eclipse –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.

6. 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.

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

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

9. 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.

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

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

12. 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.

13. Upcoming Eclipses 2014 –Lunar eclipse Oct 8 Greatest at 5:54 am CDT –Partial solar Oct 23 4:36 pm to 5:43 pm (sunset) August 21, 2017 –Total solar eclipse