Meade ETX-90PE instruction manual Planets, Deep-Sky Objects

Tip:

Enter a date in the Date menu and you can determine if a planet(s)— or any other object in the database—will be visible during the night of the entered date.

After entering a new date, go to the Object menu and select the desired planet from the menu. Then keep pressing one of the Scroll keys until the rise and set times display. Press MODE to exit.

Fig. 58: The planet Jupiter. Jupiter's four largest moons can be observed in a different position every night.

Fig. 59: Saturn has the most extensive ring struc- ture in our Solar System.

Fig. 60: The Pleiades is one of the most beautiful open clusters.

Planets

Planets change positions in the sky as they orbit around the Sun. To locate the planets on a given day or month, consult a monthly astronomy magazine, such as Sky and Telescope or Astronomy. Listed below are the best planets for viewing through your ETX model telescope.

Venus is about nine-tenths the diameter of Earth. As Venus orbits the Sun, observers can see it go through phases (crescent, half and full) much like those of the Moon. The disk of Venus appears white, as sunlight is reflected off the thick cloud cover that com- pletely obscures any surface detail.

Mars is about half the diameter of Earth. Through the telescope it appears as a tiny reddish-orange disk. You may see a hint of white at one of the planet’s polar ice caps. Approximately every two years, when Mars is closest to Earth, additional detail and coloring on the planet's surface may be visible.

Jupiter (Fig. 58) is the largest planet in our solar system, with a diameter 11 times that of Earth. Jupiter appears as a disk with dark lines stretching across the surface. These lines are cloud bands in the atmosphere. Four of Jupiter’s 29 (and still counting!) moons (Io, Europa, Ganymede and Callisto) can be seen as star-like points of light when you use even the lowest magnification. The number of moons visible on any given night changes as they circle around the giant planet.

Saturn (Fig. 59) is nine times the diameter of Earth and appears as a small, round disk with rings extending out from either side. In 1610, Galileo, the first person to observe Saturn through a telescope, did not understand that what he was seeing were rings. Instead, he believed that Saturn had “ears.” Saturn’s rings are composed of billions of ice particles. The major division in Saturn's rings, called the Cassini Division, is generally visible through all three ETX models. Titan, the largest of Saturn’s moons, can also be seen as a bright, star-like object near the planet.

Deep-Sky Objects

You can use star charts to locate constellations, individual stars and deep-sky objects. Examples of various deep-sky objects are given below:

Stars are large gaseous objects that are illuminated by nuclear fusion in their core. Because of their vast distances from our solar system, all stars appear as pinpoints of light, regardless of the size of the telescope used.

Nebulae are vast interstellar clouds of gas and dust where stars are formed. Most impressive of these is the Great Nebula in Orion (M42), a diffuse nebula that appears as a faint wispy gray cloud. M42 is 1600 light years from Earth.

Open Clusters are loose groupings of young stars, all recently formed from the same diffuse nebula. The Pleiades (Fig. 60) is an open cluster 410 light years from Earth. Several hundred stars of the cluster are visible through your telescope.

Constellations are large, imaginary patterns of stars believed by ancient civilizations to be the celestial equivalent of objects, animals, people or gods. These patterns are too large to be seen through a telescope. To learn the constellations, start with an easy grouping of stars, such as the Big Dipper in Ursa Major. Then use a star chart to explore across the sky.

Galaxies are large assemblies of stars, nebulae and star clusters that are bound by gravity. The most common shape is spiral (such as our own Milky Way), but galaxies can also be elliptical or even irregular blobs. The Andromeda Galaxy (M31) is the clos- est spiral-type galaxy to our own. This galaxy appears fuzzy and cigar-shaped. It is 2.2 million light years away in the constellation Andromeda.

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