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The Shallow Sky

Observe The Very Inner And Very Outer Solar System

Akkana Peck


The big gas giants, Jupiter and Saturn, are emerging into the morning sky; only a few degrees apart, they make a nice sight for the early morning riser. In the last week of July, Mercury, shrinking in apparent size as it grows from crescent to half phase, joins them, with the moon moving from near Saturn on the 26th to a very slim crescent just above Mercury on the 29th.

For the more traditional nighttime astronomer, this month is a good time to get acquainted with the outer solar system. Uranus, Neptune, and Pluto are all well placed for observing in the warm summer nights. Uranus and Neptune are both in Capricornus and easily accessible to binoculars (or, in dark skies, to the naked eye in the case of magnitude 5.7 Uranus - can you spot it? Try it and let me know). Both will show small blue or green disks in most telescopes. Neptune reaches opposition on the 27th, Uranus on August 11th.

Pluto is more of a challenge. Several of us tracked it down at a Fremont Peak star party last month, using the 30", a 17.5", and a 12.5". I recommend the finder chart in the RASC Observers Handbook (which many of you have already bought at our club meetings): start at 20 Oph (a fairly easy naked-eye star from the Peak), then use binoculars to find the two almost-as-bright stars to the right and a little south of 20; since Pluto passes just north of one of the more northern of the two bright stars, it should be relatively easy to get near the field. Expect the planet to be about as bright as the faintest stars plotted on the RASC chart.

Though the inner solar system planets Venus and Mars aren't visible this month, you can get a glimpse of the brightest asteroid: 4 Vesta, in Sagittarius, brightens to magnitude 5.4 for opposition on July 16. On the 27th, Vesta should be easy to find, just 5' north of 52 Sagittarii.

Finally, this is a bonus month for eclipses: three of them! Unfortunately, we aren't very well positioned for any of them. The partial solar eclipse on the 1st will require a trip to the southern end of South America. On July 16, early risers can watch the very beginnings of what will be a very nice lunar eclipse from the middle and eastern Pacific.

On July 30th, we can catch a bit of a solar eclipse, right at sunset. From the bay area, we'll see less than 15% of the sun eclipsed. Locations farther north will see more of the sun eclipsed, up to 50% in northern Canada. As always, use a solar filter when you look at the sun, especially when using binoculars or a telescope: 10% of the sun doesn't remove any of the danger. This is a also a good chance for photographers to try for eclipsed-setting-sun photos ... be creative, and bring your results to the SJAA slide & equipment night in September to show us what you got!


Mail to: Akkana Peck
Copyright © 2000 San Jose Astronomical Association
Last updated: July 19, 2007

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