SJAA Ephemeris July 2009 | SJAA Home | Contents | Previous | Next

The Shallow Sky

A faint shadow of an eclipse

Akkana Peck


The big shallow-sky event this July is one that, alas, most of us won’t get to see. It’s the total solar eclipse on July 22, visible from India, China and the south Pacific. What a terrific trip that would be! I hope some of you get a chance to see it, and I’m sure we’ll be hearing reports from SJAA members who go.

Eclipses generally come in pairs – where there’s a solar eclipse, there’s often a lunar eclipse of some sort half a month earlier or later, since the moon will still be close to the ecliptic. This month is no exception, but it’s not much of an eclipse: a penumbral lunar eclipse on July 7. The penumbra is the outer band of the earth’s shadow, and compared to a bright full moon, it’s very subtle. Worse, this time the penumbra will just barely graze the edge of the moon, making it very unlikely the shadow will be visible at all. But if you’re still up between 1:30 a.m. and 3:30 on the morning of July 7, why not check and see if you can detect anything? If nothing else, you’ll see the unusual sight of a truly full moon with no terminator at all.

Back at home, Saturn hangs in the early evening sky, unusually faint at magnitude 1.1, and sets a bit before midnight. Its rings are now tilted about 5 degrees from us and it should continue to give a nice view even if it’s not as high as it was a few months ago.

Jupiter rises around 10, moving toward its opposition around the middle of next month, and so is at its best after midnight. On the night of the 13th, it passes very close to Neptune, only about half a degree away, so you should be able to see them in the same field. Neptune is only magnitude 7.8, compared with 6.7 for the faintest Galilean moon, Callisto, and it’s due north of Jupiter rather than in line with the moons, so you won’t be tempted to mistake it for a Jovian satellite. (Galileo saw Neptune twice near Jupiter, two centuries before its discovery as a planet, and drew it as a fixed star.) It should be interesting to see the blue-green disk so near Jupiter.

Uranus, near the Pisces/Aquarius border, rises about an hour and a half later and is visible for late evening viewers.

Venus is in the morning sky, rising nearly an hour and a half before the sun. Mars is nearby, and on the morning of the 18th, early risers can get a nice naked-eye view of Venus, Mars, a crescent moon, the Pleiades and Hyades. For extra credit, compare Mars’ color to the Aldebaran. They’re pretty close to the same magnitude, with Mars at 1.1 just slightly fainter than Aldebaran’s 1.0. Which one looks redder? Does the answer change if you use binoculars or a telescope?

Mercury is invisible most of this month, too close to the sun, but emerges barely into the evening sky by the end of the month.


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