Lunar Eclipse Q & A

What causes a Lunar Eclipse ?

A lunar eclipse happens when the Moon passes through the Earth's shadow. Earth always has a shadow, which is created by the Sun. On those rare occasions when the Moon, Earth and the Sun are all lined up just right, the Moon passes through this shadow.This would happen every full moon if the Moon orbited around the Earth in the same plane as the Earth orbits around the Sun. The Moons orbit, however, is tilted about 5 degrees above the Earth-Sun plane. This tilt itself, however, rotates, allowing eclipses to happen when the tilt of this plane lines up with the Earth-Sun plane, blocking sunlight.

An eclipse of the Moon can only take place at Full Moon, and only if the Moon passes through some portion of the Earth's shadow. The shadow is actually composed of two cone-shaped components, one inside the other. The outer or penumbral shadow is a zone where some portion of the Sun's rays are blocked. In contrast, the inner or umbral shadow is a region devoid of all direct sunlight.

When can one view an eclipse ?

A lunar eclipse is visible over an entire hemisphere and is seen at the same time to everyone who is in sight of the full moon. Because of local time zones, however, the times of a lunar eclipse can span many hours.

How long does an eclipse last ?

Lunar eclipses can last for more than three hours because the Moon and the Earth are moving slowly in relation to each other, and the shadow cast by the Earth is so large. Because of their sizes and the relative distances between the Earth, Moon, and Sun, this shadow is much larger than that cast by the Moon on the Earth (during a solar eclipse).

Are all eclipses the same ?

Although eclipses are always caused by the same general lineup of Sun, Moon, and Earth, each lunar eclipse may have its own unique visual characteristic. Colors and the deepness of the shadow on the surface are affected by the type of eclipse, local weather conditions, atmospheric conditions, and the geographic location of the observer. When the Moon is in the darkest part of Earth's shadow, or in totality, it can have some beautiful colors, usually a dark pastel, such as violet or a very dark apricot.

What are the three types of eclipses?

Partial Lunar Eclipse

A portion of the Moon passes through the Earth's umbral shadow. These events are easy to see, even with the unaided eye.

Penumbral Lunar Eclipse

The Moon passes through the Earth's penumbral shadow. These events are subtle and quite difficult if not impossible to observe. During a penumbral eclipse the moons light is dimmed but does not go dark due to the fact that the penumbral shadow is not dark enough to black out the sun's light. A penumbral eclipse is sometimes referred to as an appulse eclipse.

Total Lunar Eclipse

The entire Moon passes through the Earth's umbral shadow. During the time of totality the moons color may change to a dull copper tone, an effect caused by earth shine or reflected earth light. The moon can stay in the umbrals shadow for as long as 90 minutes.

Partial Eclipse Total Eclipse Penumbral Eclipse A. Moon enters penumbra A. Moon enters penumbra A. Moon enters penumbra B. Moon enters umbra B. Moon enters umbra B. Middle of eclipse C. Middle of eclipse C. Total eclipse begins C. Moon leaves penumbra D. Moon leaves umbra D. Middle of eclipse   E. Moon leaves penumbra E. Moon leaves umbra     F. Moon leaves penumbra

Lunar Eclipse Demo

The Earth's shadow has darker and lighter areas, which you can see by watching the animated GIF below. As the Moon passes through the Earth's shadow, you can see the Moon's face get darker and darker as the shadow crosses its face, until the Moon is almost completely dark.
	Even when the Moon is in the darkest area of the Earth's shadow, though, there is still some light on the Moon's surface. This is caused by the fact light from the Sun bends slightly as it hits the Earth's atmosphere. This fact, along with the fact that light always bends around things it hits, casts a faint light on the Moon.
When the Moon is in the darkest part of Earth's shadow, or in totality, it can have some beautiful colors, usually a dark pastel, such as violet or a very dark apricot.

Lunar Eclipse Dates

     A list of lunar eclipse dates 2001 - 2003

2001 Eclipses Year Month-Day Type 2001 Jan. 9th Total 2001 Jul. 5th Partial 2001 Dec. 30th Penumbral

2002 Eclipses Year Month-Day Type 2002 May 26th Penumbral 2002 Jun. 24th Penumbral 2002 Nov. 19th Penumbral

2003 Eclipses Year Month-Day Type 2003 May 16th Total 2003 Nov. 8th Total

For more detailed lunar eclipse data visit my Detailed Lunar Eclipse page.

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Photographing A Lunar Eclipse

The best advise I can give for photographing a lunar eclipse is to take as many pictures as you can at many different exposures times and f/stop settings. Most of these photographs will probably not turn out as you hoped or expected. The bottom line is that eclipse photography is an exercise in patience. As it is with most photography you must take many shots to get one or two that are good. Good luck

Lunar Eclipse Exposure Suggestions (seconds) Partial Total ISO f/5.6 f/8 f/11 f/2.8 f/8 f/11 100 1/60 1/30 1/15 2 15 30 200 1/125 1/60 1/30 1 8 15 400 1/250 1/125 1/60 1/2 4 8 800 1/500 1/250 1/125 1/4 2 4

Hints: If you have a point-and-shoot camera with a zoom lens, zoom the lens out as far as you can to get the highest possible magnification. The minimum focal length for getting a good-looking Moon is about 300 mm. Photographing an eclipse may require exposure times 4 to 1,000 times longer as compared to recording a normal full moon Short exposures are useful only during the partial stages near the beginning and end of the eclipse It would be safe to try every camera setting you've got. There's plenty of time to experiment during this leisurely event.

A very good source of information on how to photograph a lunar eclipse can be found at:
Mr. Eclipse Lunar Photography Eclipse Guide

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Lunar & Solar Eclipse Facts

Full moons are the only time lunar eclipses occur. New moons are the only time solar eclipses occur. A solar eclipse always occurs two weeks after or two weeks before a total lunar eclipse. Lunar eclipses can last for a maximum of 3 hours and 40 minutes, with the period of totality lasting for as long as I hour and 40 minutes. Solar eclipses can last for a maximum of 7 minutes and 40 seconds if they are total (at the equator), 12 minutes and 24 seconds at most if they are annular. Lunar eclipses can never happen more than three times a year. Solar eclipses happen at least twice a year but never more than five times a year. Lunar eclipses are visible over an entire hemisphere. Solar eclipses are visible in a narrow path that is a maximum of 167 miles wide (269 km). The greatest number of solar and lunar eclipses that can happen in a year is seven. At any specific geographic location on the globe, a total solar eclipse can occur only once every 360 years, on average. Solar eclipses and lunar eclipses go together in pairs. A solar eclipse is always followed or preceded by a lunar eclipse, within an interval of 14 days. Eclipses may also occur in threes, alternating lunar, solar, lunar. The characteristics of one eclipse are repeated every 18 years, I 1 days, and 8 hours, with some minor variations. This long-term rhythm is called the Saros cycle. At any given time, there may be several dozen different series of this cycle in effect.

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