October 2014 brings big sky fun: a total lunar eclipse on Oct. 8 and a partial solar eclipse on Oct. 23. Both will be visible from most of North America. The lunar eclipse will also be visiible from the Pacific Ocean and areas around it including South America, eastern Asia, and Australia, as well as most of North America.
Eclipse Science Review
A lunar eclipse happens when the Moon passes into the shadow of the Earth. Because of the needed geometry, lunar eclipses only happen during Full Moon. But, not all Full Moons produce eclipses because of the tilts of the Earth’s axis (what also causes seasons) and the tilt of the Moon’s orbit. When those line up so the Moon passes through the shadow of the Earth, you get a lunar eclipse. If it passes completely into the darkest shadow (where no direct sunlight reaches it at all, called the umbra), then it is a total eclipse. If things line up not quite right, you may only get a partial lunar eclipse. Lunar eclipses of either kind can be seen from large portions of the Earth: any part for which the Moon is visible during eclipse. The whole process of a total lunar eclipse lasts for a few hours. The Moon often turns a shade of red during totality, like in the picture shown above that I took during the total lunar eclipse earlier this year. That color is from the light being refracted, or bent, through the Earth’s atmosphere. Poetically, it is the light of all the sunrises and sunsets of the world. Aww, how sweet. Just like with observing sunsets, it is the longer wavelength red light that makes it through lots of Earth atmosphere, and the blues get scattered away.
A solar eclipse happens when the Moon passes between the Earth and the Sun, in other words, when the Moon casts a shadow on the Earth. It has the same limitation that all the tilty stuff has to be lined up for an eclipse to happen. Because of the required geometry, solar eclipses always happen at New Moon – when the Moon is between the Earth and the Sun. The Moon’s shadow is much smaller than the Earth’s shadow, so only a portion of the Earth along the right line will see any kind of solar eclipse. The line across the Earth that would see totality, total coverage of the Sun by the Moon, is very small. When there is a total solar eclipse, a wider region can see a partial solar eclipse, areas within the penumbra where only part of the Sun is blocked by the Moon. Or, as is the case with the Oct. 23, 2014 solar eclipse, things don’t line up quite right for a total lunar eclipse, so no one sees totality, but a region of Earth can see a partial solar eclipse.
Want a little more explanation: watch the first ten minutes or so of my online lecture from last Spring semester done with California State University Dominguez Hills (more class info here).
Lunar Eclipse October 8, 2014
A total lunar eclipse occurs October 8, 2014. For those in the Americas, remember this is the night that stars on Tuesday, October 7, but the eclipse will be after midnight, so on October 8. As mentioned, the lunar eclipse will also be visible from the Pacific Ocean and areas around it including South America, eastern Asia and Australia, as well as most of North America. The Moon will set during eclipse for eastern North America and South America. Eastern most Asia and eastern Australia will see the whole eclipse, but other parts of those continents will have the Moon rise already in eclipse.
The times of the key events of the eclipse are shown in the table below. The table and the diagram refer to entry and exit from the penumbra. The penumbra is a much fainter shadow – part of the sunlight still falls directly on the Moon. If you were on the moon, you would see a partial solar eclipse when you are in the penumbra, but a total eclipse would be when you are in the umbra. The umbra is the good part for the casual observer. It will be hard to detect the dimming in the penumbra, but quite obvious when the Moon starts entering the umbra. So, for the casual observer, I’d focus on the umbra entering time, the start and end of total eclipse – when the Moon is fully within the shadow – and the time the Moon leaves the umbra which will appear to the end of the eclipse.
Penumbral Eclipse Begins:
Partial Eclipse Begins:
Total Eclipse Begins:
Total Eclipse Ends:
Partial Eclipse Ends:
Penumbral Eclipse Ends:
If you get clouded out, know that two more total lunar eclipses are in our near future. Since eclipses are tied to periodic orbits, not surprisingly, things go in cycles. Periodically we get a set of four total lunar eclipses in a row, given the fun name “tetrad”. This will be the second of four in the tetrad, the next two occurring in 2015.
All you need to observe a lunar eclipse is your eyes. And, unlike a solar eclipse, you can stare all you want. It is always fun to use binoculars or a telescope to observe the Moon, but they aren’t needed.
Solar Eclipse October 23, 2014
The partial solar eclipse will be visible from all but the most northeastern parts of North America. Unlike a lunar eclipse, the times for seeing a solar eclipse depend upon where you are because the Moon’s shadow is moving across the surface of the Earth as the Moon, and Earth, move in their orbits. You can find local times and circumstances for this partial solar eclipse by clicking here for the USA and here for Canada and Mexico.
And, oh yeah, important safety tip: DON’T STARE AT THE SUN! And, those cool looking sunglasses you have are not sufficient. As a reminder, the Sun is really bright. To observe a partial solar eclipse safely you need to either put a filter – a professional, safe filter between you and the Sun, or observe it indirectly, e.g., by projecting an image of the partial solar eclipse, which is easier than it sounds. The projection can be as easy as putting a pinhole through some cardboard and turning the cardboard perpendicular to the Sun’s light, and project the resulting image onto some paper or a wall. The pinhole effect can be caused by other things including the spaces between leaves of trees projecting lots of partially solar eclipsed Suns such as the image I got below during the 2012 annular/partial eclipse.
I am sure any number of solar observatories and the like will be providing internet images as well, which will work even for those of you who do not happen to be in the right part of the world for this particular eclipse. Learn more on observing these eclipses and on eye safety at the links below. And, have fun observing!