Appendix D: Basic Astronomy - Meade ETX-80AT-BB Instruction Manual

APPENDIX D: BASIC ASTRONOMY

In the early 17th century, Italian Scientist Galileo, using a crude telescope considerably small-
er than the ETX-80AT-BB, 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 astronomy. 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 plan-
ets, stars, and galaxies. Building on his foundation, Henrietta Leavitt determined how to meas-
ure 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, more and more
mysteries of the universe are being solved and understood. We are living in a golden age of
astronomy.
Unlike other sciences, astronomy welcomes contributions from amateurs. Much of the knowl-
edge 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 Meade ETX telescope, keep in mind Galileo. To him, a telescope was not a mere machine
of glass and metal, but something far more - a window through which the beating heart of the
universe might be glimpsed, a fuse to set fire to mind and imagination.
AutoStar Glossary
Be sure to make use of AutoStar's Glossary feature. The Glossary menu provides an alpha-
betical listing of definitions and descriptions of common astronomical terms. Access directly
through the Glossary menu or through hypertext words embedded in AutoStar. See
MENU
Objects in Space
Listed below are some of the many astronomical objects that can be seen with the ETX-80AT-
BB:
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 surface at an
angle. It casts shadows and adds a sense of depth to the view (Fig. 31). No shadows are seen
during a full Moon, causing the overly bright Moon to appear flat and rather uninteresting
through the telescope. Be sure to use 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.
Using the ETX-80AT-BB, brilliant detail can be observed on the Moon, including hundreds of
Fig. 31: The Moon.
lunar craters and maria, described below.
Note the deep shad-
ows in the craters. Craters are round meteor impact sites covering most of the Moon's surface. With no atmos-
phere 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 by
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 telescope on Earth are about one-half
mile across.
, page 25, for more information.
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GLOSSARY