Coordinates and Time
Coordinates
Alt-az System
Equatorial Coordinates
Observer-Based Azimuth and Consistent Altitude
No Permanent Description
Dec, RA, and Vernal Equinox
Permanent Description despite of Earth Rotation
Time
Other Coordinates
Ecliptic System
Galactic System
Conversion from one to another
Solar Time
Ture or Apparent Solar Time
Mean Solar Time
EqT = TST - MST
Dynamical Time
Univsersal Time (UT) is Greenwich Mean Time
Dynamical Time: TDT = UT + ΔT
Barycentric Dynamical Time
TAI
UTC: Leap Seconds
UT1
Sidereal Time
Sidereal Time is based on the Earth's rotation relative to the stars
Solar Day is 4 min or 0.986° longer than sidereal time
Julian Date
Calculate JD since 2000: JD=2451544.5 + 365 * (Y - 2000) + N + L
Began with January 1, 4713BC
Heliocentric Julian Date ( earth orbit motion considered)
Conparsion between Julian and Gregorian Calendar