Sky Talk August 2007: Total Eclipse of the Moon & Perseid Meteor Shower

This year’s second total eclipse of the Moon occurs on August 28th, giving many observers clouded out for the March event another chance to see one of nature’s grandest spectacles. This time, however, moongazers will have to be either early risers — or stay up quite late — all depending on your time zone. And the famed Perseid meteor shower peaks near mid-month for an added treat.

2007’s second total lunar eclipse is a predawn spectacular which takes place on the morning of August 28th. This event is visible in its entirely across the western half of North America, but watchers along the East Coast will see only the opening stages and just the beginning to totality, as our satellite sets in a brightening morning sky.

Partial eclipse begins at 4:52 a.m. EDT and the Moon becomes totally immersed in the Earth’s dark inner shadow (known as the umbra) an hour later at 5:52 a.m., staying within it for about 90 minutes. The final partial eclipse phase ends at 5:24 a.m. PDT, as the Moon slowly moves completely out of the shadow just prior to setting for observers on the West Coast.

There are several interesting things to notice as you watch this event unfold. Most obvious are the darkness of the eclipsed Moon and the range of colors displayed, both of which vary from one eclipse to another. These depend on the clarity of the Earth’s atmosphere at the time, which refracts or bends sunlight around into the umbral shadow. There have actually been eclipses so dark that the Moon remained all-but invisible during totality — and ones so pale that you had to look carefully to see that there was even an eclipse in progress! Among the colors that have been seen are pale orange, copper, rose, and even blood red. Notice too that the Earth’s shadow is curved at all phases of the eclipse, as the Moon passes through it. This is direct proof that the Earth itself is round — something recognized by many early skywatchers. And finally, realize that you’re actually seeing our lovely satellite move eastward in its orbit — as it first passes into, through, and then out of the shadow at roughly its own diameter each hour.

While lunar eclipses can certainly be enjoyed with the unaided eye alone, they are best-seen in binoculars. Telescopes, with their relatively narrow fields of view, typically don’t provide enough sky coverage around the Moon to get the full effect of its globe being suspended in space. An exception here is Edmund Scientifics’ marvelous Astroscan wide-field reflecting telescope. It provides a 3-degree actual field of view at a magnification of 16x, which is an astounding six full-Moon-diameters of sky!

No sky coverage for August would be complete without mentioning one of the most famous of all annual meteor showers — the Perseids! Peak activity of some 60 “shooting stars” an hour will happen on the night/morning of August 12/13th, with maximum activity occurring in the pre-dawn hours. This year’s display will have no interference from the Moon, which will be at its new phase and invisible at the time.

–James Mullaney
Former assistant editor at Sky & Telescope and author of five books on stargazing.

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