  |
|
|
|
We have some eclipses going on in April: a total-annular eclipse of the sun on the 8th, which is visible across the Pacific Ocean, Panama, Colombia, and Venezuela, and a penumbral eclipse of the moon on the 24th, visible from the western half of North America. What? Annular? Penumbral? What happened to good ol' total and partial eclipses?
Well, the solar eclipse, as I noted, is total and annular, and a penumbral eclipse is kind of partial, but not really. An annular eclipse occurs because the moon, so much nearer to us than the sun and thus the same apparent size of the sun, is not exactly the same apparent size as the sun. Not always, anyway. The difference in their apparent sizes is due to our distance from the moon. When there is a total eclipse of the sun when we are nearest the moon, the moon completely covers it. When there is a total eclipse of the sun and we are more distant from the moon, the moon does not completely cover the sun, sort of fitting within the area of the sun's width. This allows a ring of sunlight to cascade around the outline of the moon. What a sight that is. That is what we have on the 8th. The annular part, visible east of New Zealand, lasts for 10 minutes. A penumbral eclipse of the moon, on the other hand, is anything but spectacular. Some observers, in fact, don't even consider it an eclipse at all. Certainly not one that's visible, anyway. The penumbra, you see, isn't much of a shadow at all. It's a kind of outer edge to a shadow, a marginally less bright bit, not only not nearly as dark as the umbra, or shadow, but not dark enough to even be noticeable. We don't notice this kind of an eclipse because the moon gets darker, we notice this kind of eclipse because the math tells us it's going on. The moon doesn't look any darker at all. If you live in western North America, and want to see for yourself, here is the timetable for this eclipse: The moon's first contact with the Earth's penumbra occurs at 7:50 U.T. on the 24th. The middle of the eclipse occurs at 9:55 U.T., when the moon is nearest the center of the Earth's shadow, which isn't very near at all. And at 12:00 U.T., the eclipse ends. Pretty boring, huh? Go To Page: 1 2 |
|
|
|
