Looking at or near the Sun will cause instant and irreversible damage to your eye!
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APPENDIX D: BASIC ASTRONOMY
Twelve Apollo astronauts left their bootprints on the Moon in the late
1960's and early 1970's. However, no telescope on Earth is able to see
these footprints or any other artifacts. In fact, the smallest lunar features
that may be seen with the largest telescope on Earth are about one-half
mile across.
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 the Messier-Series.
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 reflec-
ted off the thick cloud cover that completely obscures any surface detail.
Mars is about half the diameter of Earth, and appears through the telesco-
pe 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 eleven times the
diameter of Earth. The planet appears as a disk with dark lines stretching
across the surface (Fig. 43). These lines are cloud bands in the
atmosphere. Four of Jupiter’s moons (Io, Europa, Ganymede, and Callisto)
can be seen as “star-like” points of light when using even the lowest
magnification. These 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 either side (Fig. 44). 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 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 Messier-Series. Titan, the largest of
Saturn’s 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. (Fig 45)
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 (Fig. 46). Through the Messier-Series, numerous stars are visible.
Fig. 44: Saturn with its ring
system.
Fig. 44a: Saturn, in a higher
magnification. It has the most
extensive ring structure in our
Solar System.
Fig. 45: A favourite Winter object:
M42, the great Orion Nebula.
