Telescopes Mastery PLR Ebook

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Chapter 5 - What to Find in the Sky

The easiest planet for a beginning astronomer to observe is the moon. The Moon has so many features and details that if you observed it each possible night for the next decade, you wouldn't see everything.

The Moon is a brilliant object when viewed through a telescope. You actually may want to use a neutral density filter to reduce the Moon's light. A better method is to do what many observers do to help them observe the Moon in comfort: Turn on nearby white lights when you're observing the Moon between First Quarter and Full.

The addition of white lights suppresses the eyes' tendency to dark adapt at night and, in fact, causes the eye to use normal (scotopic) vision, which is of much higher quality than dark-adapted (photopic) vision.

Of the 1,940 named features on the Moon, 1,545 (nearly 80 percent) are craters. There are many more craters in the highlands than in the maria. The size range of craters is large, and some observers make it a personal challenge to see either (1) how small a crater they can see, or (2) how many small craters in a given area they can observe with a particular telescope. A detailed map of the Moon is, of course, a necessity for a project of this type.

When observing larger craters, note whether you can see "rays" emanating from them. These features were formed when crushed rock sprayed out from a meteor impact. They form streaks in a radial pattern, which can be a great distance from the crater itself.

Next to the Sun and Moon, the celestial object with the greatest detail is Jupiter. Even small telescopes will show Jupiter's four largest satellites. They appear as bright stars on either side of Jupiter and are generally in a straight line (although some interesting triangles and other forms are possible).

In addition to the moons, several dark stripes can easily be seen on the planet. These stripes, on either side of the equator, are known as the North and South Equatorial Belts. With larger telescopes operating at greater magnifications, more belts are visible.

At higher magnification, you can see that Jupiter is flattened, a result of its rapid rotation rate coupled with the fact that it is not a solid planet. Jupiter's equatorial diameter is more than 5,000 miles larger than its polar diameter.

Watching Jupiter night after night can be a rewarding pursuit. In addition to the changing positions of its moons, the planet's rapid rotation brings nearly all of its visible area into view in a single night. At times, individual belts and zones become more or less prominent. Some have even disappeared for extended periods of time.

All observers should use filters to bring out fainter detail not visualized in integrated (white) light. A blue (e.g., Wratten 38A) filter will enhance the dark reddish-brown belts over the planet. A red (e.g., Wratten 23A) filter will bring out the blue features (festoons) within the Equatorial Zone (EZ) of Jupiter as well as the northern and southern borders of the major belts.

Jupiter is a great object to sketch. Sketching will make you a better observer because you'll study small areas more intently. Two words of caution when sketching Jupiter: Draw quickly! Jupiter rotates quite rapidly, and some of the features you'll be sketching may rotate out of view if you take longer than about 20 minutes.

Sketch the positions of the equatorial belts and Polar Regions first. Carefully estimate their widths and extent and where, in terms of latitude, they begin and end. Next, place the less apparent belts and zones on your sketch as they appear on the planet. Work on one hemisphere at a time.

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