51
APPENDIX B:
BASIC ASTRONOMY
In the early 17th century Italian Scientist Galileo, using
a crude telescope considerably smaller than the ETX
80, turned it to look towards the sky instead of distant
trees and mountains. What he saw, and what he
realized about what he saw, forever changed the way
mankind thought of the universe. Imagine what it must
KDYH EHHQ OLNH EHLQJ WKH ¿UVW KXPDQ WR VHH PRRQV
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 planets,
stars, and galaxies. Building on his foundation,
Henrietta Leavitt determined 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, 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 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 Meade ETX 90 telescope,
keep Galileo in mind. To him, a telescope was not
merely a machine made of glass and metal, but
something far more - a window through which the
beating heart of the universe might be observed.
Objects in Space
Listed below are some of the many astronomical
objects that can be seen with the ETX
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. No shadows are seen
during a full Moon, causing
the overly bright Moon
WR DSSHDU ÀDW DQG UDWKHU
uninteresting through the
WHOHVFRSH%HVXUHWRXVHDQHXWUDO0RRQ¿OWHUZKHQ
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, 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
DUH ODUJH DQFLHQW LPSDFW EDVLQV WKDW ZHUH ¿OOHG ZLWK
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.
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. You can
also consult ETX 90 for information about planets.
BASIC ASTRONOMY
