ASTRONOMY

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ASTRONOMY
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Chapter One "Finding your way in the dark"
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To ancient man, the sky was one of the most
noticeable objects in their world.
The sun was (and still is) the single most
important object in the sky.
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The celestial sphere is an imaginary bowl that
all objects in the sky can be looked on, as if
they are attached to it.
Light pollution from street lamps, cities, etc,
make it hard to see the night sky in urban areas.
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Modern man doesnt have the night sky that our
ancestors did.
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Our moon
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The changing phases of the moon intrigued ancient
astronomers.
Important to some religions, the phases of the
moon were important to our calendar giving us
weeks and months.
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While the stars appeared to stay fixed on the
celestial sphere, there were some exceptions.
The ancient Greeks called the five they could
see, planetes or wanderers. (Planets)
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A coordinate system is easy for earth (things do
not appear to be moving), but for a rotating
sphere, it is not so easy.
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COORDINATES!
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The Earths North pole extends upward to form the
celestial North pole.
The same is true for the South pole and the
equator.
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Declination the angular distance from the
celestial North or South polemuch like lines of
latitude on Earth.
Right ascension A coordinate used to measure the
East-West position of objects in the sky.
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Altazimuth?
Altazimuth A coordinate system used for one
location time to find objects angular height
(altitude) above the horizon and compass
direction (azimuth) measured in degrees from due
North.
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Angular size vs. angular separation
Astronomers must talk about size and separation
in terms of apparent.
Both are measured in angular degrees.
1 degree 60 arcminutes.
1 arcminute 60 arcseconds.
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Constellations
Constellations are perceived images in the night
sky, made by the connecting of stars.
(There are 88 of them.)
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Constellations serve as landmarks in the sky.
Whats your sign?
There are 12 called the zodiac constellations.
They lie along the ecliptic (the suns path
through the sky).
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Asterism?
An asterism is a group of stars inside of
constellation that form a recognizable shape.
The little dipper is within the constellation
of Ursa Minor.
The 7-sisters (Pleiades) is within the
constellation of Taurus.