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January 23, 2023

Backyard Astronomy: Summer constellations revisited (2003-10-06)

By Cheryl Haimann

October is a strange month for stargazers. The weather is fine for viewing. The cooler temperatures beat down the mosquitos and other pests. The humidity may be less intense, making for clearer, steadier skies, especially if you are using a telescope or binoculars. Earlier sunsets give you more time to view in the evening.

On the other hand, the Great Square of Pegasus, 15 degrees wide on each side, takes up a large part of the eastern sky, and the next batch of constellations are low in the sky until late in the evening. Even worse this week, the moon is waxing gibbous, between first quarter and full, and growing larger and brighter every day. Faint stars don't stand a chance with a gibbous moon.

When life gives you lemons, they say, make lemonade. In this case, try revisiting some familiar constellations from summer.

Just about everything you looked at all summer is still out there. Arcturus is low in the west at sundown, and Bootes is now standing almost straight up. The Big Dipper sits open-side up near the horizon in the early evening. As a circumpolar constellation, it never sets for those of us in the northern latitudes, but it can definitely drop out of sight if your view is obstructed by buildings or trees.

The Milky Way runs from Sagittarius, low in the southwest, through the Summer Triangle high overhead, and on towards Cassiopeia in the northeast. Hercules is already past zenith (the straight-overhead point) and heading west. If you haven't managed to see the star clusters M13 and M92 in Hercules, you might want to try again. Looking through binoculars at something overhead is an invitation for neck strain. Hercules is much better situated now for lawn chair observers.

Mars is still bright, and still in the Capricornus and Aquarius region to the southeast. These constellations are higher now than they were when Mars was at its peak in August, and thus easier to see. For the next few days, though, with the moon nearby, forget about observing these dim constellations. After the full moon on October 10, though, you may be able to make them out from a fairly dark location. Even with the moon and city lights, you should be able to see Fomalhaut, the mouth of the southern fish, Piscis Austrinus. It is almost directly below Mars. On a moony night, it will be the only star you can see in the area.

Mars, on the other hand, will dim noticeably as October progresses, losing half its brightness. Never fear, there are more planets on the horizon for winter viewing. In October, the best way to see them is to be an early riser. At 6:00 AM, Saturn is high in the south, to the left of Orion. Jupiter is low in the east, just below the sickle-shaped head of Leo. If you have a clear eastern horizon and good eyes, you may even spot Mercury in the pre-dawn twilight about 40 minutes before sunrise. It is very close to the horizon below Jupiter. Look quickly, though, as it will be dropping out of sight in a few weeks.
Article © Cheryl Haimann. All rights reserved.
Published on 2003-10-06
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