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Jupiter (Fig. 34) 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. 35) 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. 36) is an open
cluster 410 light years from Earth. Several
hundred stars of the cluster are visible through
the 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 closest 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.
TIPS
FOR BEGINNERS
Further Study....
This manual gives only the briefest introduction to
astronomy. If you are interested in pursuing further
studies in astronomy, a few topics are suggested
below that are worth reading up on. Try looking up
some of these in the optional Autostar glossary.
Also included below is a small sampling of books,
magazines, and organizations that you might find
helpful.
Topics
1. How is a star born? How does a solar system
form?
2. How is the distance to a star measured? What
is a light year? What is red shift and blue shift?
3. How are the craters on our Moon formed? How
old is the Moon and Earth? How old is the Sun?
4.
What is a black hole? A neutron star?
5. What are stars made of? Why are stars
different colors? What is a white dwarf? A red
giant? Have we ever seen the surface of a star
besides our own sun?
6. What is a nova? A supernova?
7. What are comets? Minor planets? Meteors?
Meteor showers? Where do they come from?
8. What is a planetary nebula? A globular cluster?
9. What is the Big Bang? Is the universe
expanding or contracting, or does it always
remain the same? What is dark matter?
10. What is an extrasolar planet? What is an
accretion (or protoplanetary) disk?
11. What is the difference between an elliptical, a
spiral, and an irregular galaxy?
Books
1. The Guide to Amateur Astronomy by Jack
Newton and Philip Teece
2. The Sky: A User’s Guide by David Levy
3.
Turn Left at Orion by Guy Consolmagno & Dan
Davis
4. Astrophotography for the Amateur by Michael
Covington
Magazines
1. Sky & Telescope
Box 9111, Belmont, MA 02178
2. Astronomy
Box 1612, Waukesha, WI 53187
Organizations:
1. Astronomical League
Executive Secretary
5675 Real del Norte, Las Cruces, NM 88012
2. The Astronomical Society of the Pacific
390 Ashton Ave, San Francisco, CA 94112
3. The Planetary Society
65 North Catalina Ave, Pasadena, CA 91106
And watch Jack Horkheimer, Star Gazer, on your
local PBS station.
Fig. 35: Saturn has
the most extensive
ring structure in our
Solar System.
Fig. 36: The
Pleiades is one of
the most beautiful
open clusters.
Fig. 34: Jupiter and
its four largest
moons. The moons
can be observed in
a different position
every night.