By Larry Mahon

Agate Ridge observatory

Venus still appears low in the west southwest shortly after sunset again this month. The interesting feature about this is that it is brightening from -4.0 to -4.2 magnitude while less of the planet is sunlit.

It is in the gibbous phase and the sunlit face shrinks from 74 to 64 percent. On Sept. 8, the crescent moon passes south of Venus. In Brazil, some places will see a short occultation at sunset.

Saturn starts the month 18 degrees to Venus’s upper left. The gap between the two planets reduces rapidly. Their closest approach to each other will occur on Sept. 17 and 18, when Saturn will be only 3 1/2 degrees above the much brighter Venus. Saturn sets 2 1/2 hours after sunset on Sept. 1, but only 1 1/2 hours after the sun on Sept. 30.

The sun reaches the equinox at 1:44 PDT on Sept. 22, crossing the equator moving southward to start autumn in our Northern Hemisphere. Summer will be officially over.

Jupiter rose at 1:43 a.m. on the morning of Aug. 31, followed by Mars at 3:11 a.m. Jupiter is moving westward faster than Mars. By the end of the month Jupiter rises at 12:06 a.m. and Mars at 2:52 a.m.

Mars has two interesting conjunctions this month. The first one is its passage through the Beehive star cluster (M-44) on the mornings of Sept. 8 and 9. You will need a telescope to see the star cluster clearly. The second conjunction is with the very dim comet C/2012 S1 ISON on the morning of Sept. 27, when it will be just 2.0 degrees north of Mars. The question is, will the comet reach 10th magnitude, which would be visible in a small telescope?

“Comet ISON Approaches” is the title of the latest article in Sky and Telescope about the comet. It is written by John Bortle, a contributing editor for comet topics since 1967. The extensive article concludes with this and I quote him, "Will it be the `comet of the century?’ If we’re talking only about Northern Hemisphere observers, and since the century is only 13 years old, there is still a chance."

To keep up to date with Comet ISON and its developments, go to Happy viewing.

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