SOLAR AND LUNAR ECLIPSE PAGE

A solar eclipse occurs when the Moon passes between the Sun and Earth, casting the Moon's shadow on Earth.  A solar eclipse can only happen during a New Moon.  The Moon's orbit is titled 5 degrees to Earth's orbit around the Sun.  Therefore a solar eclipse is a relatively rare phenomena and a Total or Annular eclipse even more rare.  

To understand the difference between a Total and Annular eclipse of the Sun, we must state that the Moon has an elliptical orbit around Earth.  In fact, the Moon's distance from Earth varies from a minimum of 221,000 to a maximum of 252,000 miles.  Therefore the Moon's apparent size in our sky will vary by 13%.  When the Moon's orbit is toward its minimum distance from Earth, the Moon will appear visually as a larger disk than the Sun.  If an eclipse occurs during this time, it will be a Total solar eclipse because the Moon has totally obscured the Sun's disk, producing the beautiful solar corona ejecting outward from the Sun.  One important element to remember though is that the Moon's shadow will obviously become narrower as it is cast from the Moon to Earth (in a shape of a cone with the wide end being at the Moon and the narrow end on Earth).  Therefore the path of totality on Earth is narrow.  It is also very short-lived as the Moon is moving quickly away from its perfect location of being situated between the Sun and Earth. 

An Annular solar eclipse is different than Totality in that it occurs when the Moon is closer to its maximum distance from Earth in its orbit.  If an eclipse happens during this situation, the Moon will appear visually smaller than the Sun and its shadow cast will not be long enough to reach Earth.  What reaches Earth is the antumbral or "negative" shadow.  If you are within the antumbral shadow, you will see a solar eclipse where a thin ring or annulus of bright sunlight surrounds the Moon.  Therefore Annular solar eclipses are still spectacular in that they are almost Total, but the solar corona is not seen due to the brightness of the annulus.  Like a Total eclipse, the Annular solar eclipse will have a narrow path on Earth with short duration, most often less than 10 minutes. 

DO NOT observe a solar eclipse with the naked eye.  Serious eye damage can result.  Use approved solar filters (camera film negatives do not count) or cut a pin hole in a shoe box and watch the Sun's light cast through the pin hole onto a smooth surface such as cardboard.

DATES OF TOTAL AND ANNULAR SOLAR ECLIPSES AND LOCATIONS OF BEST VIEWING THROUGH 2020

DATE

ECLIPSE TYPE

GREATEST ECLIPSE CENTRAL DURATION

FRACTION OF SUN'S DIAMETER OBSCURED BY THE MOON

LOCATIONS OF GREATEST SOLAR OBSCURATION

03/20/2015 Total 2 min 47 sec 1.045 North Atlantic, Arctic Ocean
03/09/2016  Total   4 min 9 sec  1.045 Sumatra, Borneo, Equatorial Pacific 
09/01/2016  Annular   3 min 6 sec  0.974  Equatorial Atlantic, South Africa, Madagascar, South Indian Ocean
02/26/2017 Annular 0 min 44 sec 0.992 Southeast Pacific, Southern South America, South Atlantic, Southwest Africa
**08/21/2017** Total 2 min 40 sec 1.031 North Pacific, U.S., Central Atlantic
07/02/2019 Total 4 min 33 sec 1.046 South Pacific, Southern South America
12/26/2019 Annular 3 min 39 sec 0.970 Saudi Arabia, Southern India, Sumatra, Borneo
06/21/2020 Annular 0 min 38 sec 0.994 Central Africa, South Asia, China, West Pacific
12/14/2020 Total 2 min 10 sec 1.025 South Pacific, Southern South America, South Atlantic

** Eclipse Visible in United States

Data calculated by Fred Espenak, NASA Goddard Space Flight Center.

Precise solar eclipse paths and detailed solar eclipse information can be obtained from Fred Espenak's site at NASA GSFC.  


 

A Lunar eclipse occurs when the Sun casts Earth's shadow onto the Moon.  For this to happen, the Earth must be physically between the Sun and Moon with all three bodies lying on the same plane of orbit.  A lunar eclipse can only occur during a Full Moon and when the Moon passes through all or a portion of Earth's shadow.  

The outer portion of the shadow cast from Earth is known as the penumbral shadow, which is an area where Earth obstructs only a part of the Sun's light from reaching the Moon.  The umbral shadow is the "inner" shadow, which is the area where Earth blocks all direct sunlight from reaching the Moon.  A penumbral lunar eclipse is subtle and very difficult to observe.  A partial lunar eclipse is when a portion of the Moon passes through the Earth's umbral shadow.  Finally, a total lunar eclipse is when the entire Moon passes into the Earth's umbral shadow.  During a total lunar eclipse, the sequence of eclipses are penumbral, partial, total, partial and back to penumbral.  

Unlike solar eclipses, a total lunar eclipse lasts a few hours, with totality itself usually averaging anywhere from about 30 minutes to over an hour.  This is due to the large relative size of Earth over the Moon (the Moon's diameter is only about 2150 miles), therefore casting a large umbral shadow on the Moon.  In addition, lunar eclipses are more frequent than their solar counterparts.  There are zero to three lunar eclipses per year (although possibly not all at the same location on Earth) where the Moon passes through at least a portion of the Earth's umbral shadow (producing a partial to total eclipse).  As stated above in the solar eclipse explanation, the Moon's orbit is tilted 5 degrees from Earth's orbit.  For an eclipse to occur, the Moon and Earth have to be on the same orbital plane with the Sun, so the Earth's shadow can be cast onto the Moon from the Sun.  This is why lunar eclipses only occur on average one or two times a year instead of every month.  

Even though the Moon is immersed in the Earth's umbral shadow, indirect sunlight will still reach the Moon thus illuminating it slightly.  This is because indirect sunlight reaches the Moon and also the Earth's atmosphere will bend a very small portion of sunlight onto the Moon's surface.  Many times during lunar totality, the color of the Moon will take on a dark red hue or brown/orange color.  As sunlight passes through Earth's atmosphere, the blue-light is scattered out.  The amount of illumination of the Moon will vary depending on how much dust is in the Earth's atmosphere.  The more dust present in the atmosphere, the less illuminated the Moon will be. 

Lunar eclipses are totally safe to be viewed by the naked eye, through binoculars or a telescope.

Below is a table of total lunar eclipse information visibile in the United States through 2020 obtained from  Fred Espenak's site at NASA GSFC

 

DATE

OVERALL ECLIPSE DURATION

TOTALITY ECLIPSE DURATION

FRACTION OF MOON'S DIAMETER OBSCURED BY EARTH'S UMBRA

NOTES INVOLVING ECLIPSE 

04/04/2015  3 hrs 29 min   0 hrs 5 min 1.001   Eclipse ongoing at Moonset
09/28/2015 3 hrs 20 min 1 hr 12 min 1.276 All Eclipse Visible Eastern Half of U.S.
01/31/2018 3 hrs 23 min 1 hr 16 min 1.315 Eclipse ongoing at Moonset
01/21/2019 3 hrs 17 min 1 hr 02 min 1.195 All Eclipse Visible


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