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In the early 17th century, Italian scientist Galileo, using a crude telescope smaller than
your NG or NGC, turned it to look towards the sky instead of distant trees and moun-
tains. What he saw, and what he realized about what he saw, forever changed the
way mankind thought of the universe. Imagine what it must have been like being the
first human to see moons revolve around the planet Jupiter or to see the changing
phases of Venus! Because of his observations, Galileo correctly realized Earth's
movement and position around the Sun, and in doing so, gave birth to modern astron-
omy. Yet Galileo's telescope was so crude, he could not clearly make out the rings of
Saturn.
Galileo's discoveries laid the foundation for understanding the motion and nature of
the planets, stars and galaxies. Building on his foundation, Henrietta Leavitt deter-
mined how to measure the distance to stars; Edwin Hubble proposed a glimpse into
the origin of the universe; Albert Einstein unraveled the relationship of time and light.
Almost daily, using sophisticated successors to Galileo's crude telescope, such as the
Hubble Space Telescope and the Chandra X-Ray telescope, more and more myster-
ies of the universe are being solved and understood. We are living in the golden age
of astronomy.
Unlike other sciences, astronomy welcomes contributions from amateurs. Much of the
knowledge we have on subjects such as comets, meteor showers, variable stars, the
Moon and our solar system comes from observations made by amateur astronomers.
So as you look through your telescope, keep in mind Galileo. To him, a telescope was
not a mere machine of glass and metal, but something far more—a window of incred-
ible discovery.
The Glossary
Be sure to make use of the Glossary feature in your NGC computer control panel. The
Glossary menu provides an alphabetical listing of definitions and descriptions of com-
mon astronomical terms. Access directly through the Glossary menu or through
hypertext words. See GLOSSARY MENU, page 17, for more information.
Objects in Space
Listed below are some of the many astronomical objects that can be seen with your
telescope:
The Moon
The Moon is, on average, a distance of 239,000 miles (380,000km) from Earth and is
best observed during its crescent or half phase when Sunlight strikes the Moon’s sur-
face at an angle. It casts shadows and adds a sense of depth to the view (Fig. 19).
No shadows are seen during a full Moon, causing the overly bright Moon to appear
flat and rather uninteresting through the telescope. Try using a neutral Moon filter
when observing the Moon. Not only does it protect your eyes from the bright glare of
the Moon, but it also helps enhance contrast, providing a more dramatic image.
Brilliant detail can be observed on the Moon, including hundreds of lunar craters and
maria, described below.
Craters are round meteor impact sites covering most of the Moon’s surface. With no
atmosphere on the Moon, no weather conditions exist, so the only erosive force is
meteor strikes. Under these conditions, lunar craters can last for millions of years.
Maria (plural for mare) are smooth, dark areas scattered across the lunar surface.
These dark areas are large ancient impact basins that were filled with lava from the
interior of the Moon due to the depth and force of a meteor or comet impact.
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 tele-
scope on Earth are about one-half mile across.
Planets
Planets change positions in the sky as they orbit around the Sun. To locate the plan-
ets on a given day or month, consult a monthly astronomy magazine, such as Sky
BASIC ASTRONOMY
Fig. 19:The Moon. Note the deep
shadows in the craters.