Lunar Eclipses 20022022

Lunar eclipses are an entirely different prospect: a good fraction can be seen without leaving home sweet home. Maps like that in Figure 2-5 are readily available, indicating that well over half of the globe gets to see at least part of each lunar eclipse. In the case of that specific eclipse—the one due on May 16, 2003—the global map shows that it can be viewed from the east coast of North America in its entirety, with locations further west than Chicago and Dallas seeing the Moon in eclipse as it rises.

In fact, reckoning whether you will be able to see a lunar eclipse is quite straightforward so long as you know when it will take place, in Universal Time (the correct term for what is often called Greenwich Mean Time or GMT). The sums are not difficult. Take the example of the above eclipse. Greatest eclipse is at 03:40 UT, which tells you the central longitude of the area on the Earth from which it may be seen: 3 hours and 40 minutes, which is equivalent to 55 degrees, to the west of the Greenwich meridian. This longitude passes down through Newfoundland and then through the western Atlantic, eventually meeting the land again at the northern coast of South America and then proceeding south through the middle of Brazil. Anywhere within about 90 degrees of longitude of that meridian will be able to see the complete eclipse.

There is also a latitude effect, however, due to the tilt of our spin axis. This eclipse will take place five weeks before the summer solstice, when the Northern Hemisphere is tipped towards the Sun during the day, which means that it is tipped away from the Moon in opposition at night. Thus more southern latitudes are favored (as is clear from Figure 2-5), the converse being true for an eclipse during the winter. Simply put, you are more likely to see a lunar eclipse during a long winter night than a short summer night. There's not much more to it.

Unlike totality in a solar eclipse, which is brief and striking, a total lunar eclipse is more protracted, typically lasting from 60 to 80 minutes. Such eclipses are certainly dramatic in their own way, but they have neither the rarity value, nor the effects on animals and humans alike, that distinguish solar eclipses. Nevertheless they are well worth watching, when the chance arises, so let us summarize the circumstances for the first seven total lunar eclipses in Figure 15-6, through to the year 2010. All times given are in Universal Time. In the United States one needs to knock five hours off for Eastern Standard Time, and so on through to eight hours for Pacific Standard Time.

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