Tilt, not distance makes a difference

Monday, July 9, 2007

The Earth was at its farthest point from the Sun for the year on July 6, did you feel any colder? As discussed before, the Sun being so far away has nothing to do with the seasons -- or earthly temperatures. Rather the tilt of the Earth on its axis at this time of the year points the northern hemisphere toward the Sun, so sunlight shines more directly on our part of the planet.

Did you find the Coathanger Cluster? Well, it will be up all summer so keep trying. It is a nice, if unusual, viewing object.

How about another binocular challenge? This one takes place in the daytime. Go out about 10:30 or 11:00 in the morning on Tuesday, July 17, and look due east about halfway between the Sun and the horizon. You should find a two-day old crescent Moon and the planet Venus. CAUTION: BE VERY CAREFUL NOT TO ACCIDENTALLY POINT YOUR BINOCULARS TOWARD THE SUN!

The summer constellations Sagittarius, with its distinctive "teapot" shape, and Scorpius, a giant "J" or fish hook shape, are at their glorious peak in the south each evening, along with the bright planet Jupiter.

This region of the sky is marvelous to scan with telescopes or binoculars. Here, looking towards the center of the Milky Way galaxy, you can find many star clusters, glowing nebula, and black patches known as "dark nebulae."

All you have to do is find a dark place, a comfortable place to sit, something for a snack and to drink. Don't forget the insect repellent!

You will have all the ingredients for an enjoyable evening under the stars.

SKY WATCH: New Moon on Saturday, July 14. Two nights later you will get another chance to view a close conjunction of the Moon and a couple of planets and a star thrown in for good measure. Look to the west about 45 minutes to an hour after sunset for a joining of a very slender crescent Moon and dim Saturn on the right and bright Venus on the left.

Up and slightly to the left of the Moon will be Regulus, the brightest star in Leo, the Lion appearing about as bright as Saturn. All four will almost fit inside the field of view of a pair of binoculars. The following evening the Moon will move off to the left (east) leaving Saturn, Venus and Regulus in a close triangle.

Saturn is so dim because it is about to travel to the far side of the Sun as seen from Earth, about as far away as it can get. Mars is moving closer to the Earth as it returns from from the far side of the Sun, thus growing brighter each morning.

Swift Mercury is also making a showing in the morning sky. Mars is about as far above bright Aldebaran in Taurus, the Bull, as Mercury is below it.

Next time, more ramblings about astronomical stuff.

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