Filter
Top Products
58
Fig. 56: The Pleiades is
one of the most beautiful
open clusters.
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.
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
completely 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. 54) 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. 55) 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. 56) 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.
Fig. 55: Saturn has the
most extensive ring struc-
ture in our Solar System.
Fig. 54: The planet Jupiter.
Jupiter's four largest
moons can be observed in
a different position every
night.