Chapter 2 Flashcards
(29 cards)
Apparent solar time
keeping time according to the position of the sun in the sky
Autumnal equinox
point the sun crosses the celestial equator and has 0 declination
Celestial equator
90 degrees from both poles. divides the sky into north and south
Conjunction
when a planet is nearly aligned with the sun
Declination
a north south coordinate equal to the angular distance of a star from the celestial equator
Direct motion
see prograde
Diurnal
daily
Diurnal circle
the path a star appears to follow
Ecliptic
path sun follows among the stars
Equatorial system
a coordinate system similar to earth for the sky
leap years
adding an extra day once every four years
local hour angle
angular distance westward around the celestial equator from the meridian to the point on the equator nearest the star
mean solar time
average solar time classic 24hr days.
meridian
the line that passes through both celestial poles and the zenith and divides the sky into east and west
nodes
points of intersection between the ecliptic and the moons orbit
opposition
when a planet is opposite of the sun
prograde motion
planet moves eastward
retrograde motion
that time when the planets motion eastward appears to reverse westward
right accension
angular distance measured eastward along the celestial equator from the vernal equinox
sidereal clocks
used to keep track of the vernal equinox. o hours when the vernal crosses the meridian 24 when it returns to the meridian
Sidereal day
length of time it takes a star to return to the meridian
Sidereal month
time it takes the moon to return to the same place among the stars
Summer solstice
point on the ecliptic where the sun is most northernly
synodic month
length of time it takes the moon to return to the same position relative to the sun.
