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From Earth’s Perspective:
Celestial Motion:
Stellar Motion
Solar Motion
Planetary Motion
Some stars and constellations
Are circumpolar—never rise or set.
Constellation vs Asterism!
A constellation is one of
88 listed ‘states’ or regions
in the sky: like Orion.
An asterism is not on the list
Of 88, but forms a shape
In the sky: like the Big Dipper,
Part of the constellation Ursa
Finding Planets:
Once you find the North Star,
Turn around 180 degrees—
The Ecliptic and the planets
will be in the sky toward the South.
The stars (at a given time of night) shift 1 degree a day
Because the earth is orbiting the sun.
Thus the sidereal day is 23 hours and 56 minutes:
It is the time for a star to return to the same place
In the sky.
Solar motion:
Mean solar day--24 hours by definition.
Return of sun to same angle of view relative to the horizon.
seasons caused by tilt of earth’s axis,
solstices--maximum and minimum light,
equinoxes equal light on northern and southern hemisphere.
Planetary motion:
retrograde motion--apparent backtracking of
planets in sky from earth's perspective.
inner planets--Me and Ve
--stay within 'maximum elongation'.
conjunction vs opposition
Mercury 8/30/02
Above Cloud Center
w/ Venus Upper Left