Locate the celestial equator. Name one star on or very near it. Find one within 10 degrees north or south.______ is about _____ degrees N/S of the equator. Indicate in your answer if the star is north or south.
Distances on the sky are measured in terms of angles. Lines from
opposite sides of the Moon to your eye intersect at an angle of about 1/2
degree, so we say the Moon spans, orsubtends, an angle of
about 1/2 degree. Your fist at arm's length spans about 10 degrees.
The heavens appear to rotate around two points called thecelestial
poles. The elevation of the pole above your horizon is equal to
your latitude. Stars close to the north celestial pole circle the pole without
ever hitting the horizon. Such stars are calledcircumpolar.
Around the South Celestial Pole is a similar zone of stars that never rise. In
between, is a band of stars that rise and set.
Since the celestial pole is at an elevation equal to your
latitude, at the North Pole the elevation of the celestial pole is 90 degrees -
straight overhead. All the stars circle the pole endlessly and never rise or
set. All the stars are circumpolar, and the opposite half of the sky can never
be seen. At the equator, the poles are at an elevation of zero degrees. All
stars rise and set. The equator is the only latitude where all stars in the sky
are visible at some time or another.
On the star maps below, major constellations are joined by red
lines, and less conspicuous constellations are in gray. Not all constellations
are shown. Constellations are in bold type, individual stars andasterisms,
or informally named groups of stars, are in italics
Feb 3rd, 2015
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