Scroll to the “Object: Solar System” menu and scroll
through the lists of planets. When a planet you are
interested in displays, press “ENTER”. Use the Scroll
keys to display information about the planet, such as
the planet’s coordinates, and the rise and set times
(Tip: enter a date in the Date menu and you can
determine if a planet) will be visible during the night
of the entered date by checking its rise and set times).
Listed below are the best planets for viewing through
the ETX 90/125.
Mars is about half the diameter of Earth, and appears
through the telescope as a tiny reddish-orange disk.
It may be possible to see a hint of white at one of the
planet’s Polar ice caps. Approximately every two years,
when Mars is closest to Earth in its orbit, additional
detail and coloring on the planet’s surface may
be visible.
Jupiter is the largest planet in our solar system and
is 11 times the diameter
of Earth. The planet
appears as a disk with
dark lines stretching
across the surface. These
lines are cloud bands in
the atmosphere. Four of
Jupiter’s 16 moons (Io,
Europa, Ganymede, and
Callisto) can be seen as
“star-like” points of light
when using even the lowest
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moons orbit Jupiter so
that the number of moons visible on any given night
changes as they circle around the giant planet.
Saturn is nine times the diameter of Earth and appears
as a small, round disk with rings extending out from
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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 ranging in size from a speck
of dust to the size of a house. The major division in
Saturn’s rings, called
the Cassini Division,
is occasionally visible
through the ETX 90. Titan,
the largest of Saturn’s 18
moons can also be seen
as a bright, star-like object
near the planet.
Deep-Sky Objects
Star charts can be used
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 self-
illuminated by nuclear fusion in their core. Because
of their vast distances from our solar system, all stars
appear as pinpoints of light, irrespective 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 is an open
cluster 410 light years away. Through the ETX, numerous
stars are visible. 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, located between the
large “W” of Cassiopeia and the great square of Pegasus.
BASIC ASTRONOMY
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