Altitude
—°
Angle above the horizon. Positive = daytime, negative = night. 0° = sunrise or sunset.
Declination
—°
Sun's latitude on the celestial sphere. +23.4° at June solstice, −23.4° at December solstice, 0° at equinoxes.
Right Ascension
—°
Sun's longitude on the celestial sphere (0–360°). Tells you which constellation the Sun is in. 15° = 1 hour.
Local Sidereal Time
—°
The right ascension currently crossing your local meridian. When LST = Sun's RA, it's solar noon where you are.
Hour Angle
—°
How far the Sun is from your meridian. 0° = solar noon. Negative = morning (east), positive = afternoon (west). Each 15° = 1 hour.
GMST
—°
Greenwich Mean Sidereal Time. The right ascension crossing the Greenwich meridian. "Star time" at longitude 0°.
Altitude at Noon
—°
How high the Sun gets that day. Maximum altitude ≈ 90° − latitude + declination.
Declination
—°
Changes day to day as the Earth orbits the Sun. Drives the seasons.
Right Ascension
—°
Increases by about 1° per day as the Sun moves eastward through the zodiac.
Local Sidereal Time
—°
At mean noon UTC, LST depends on the date and your longitude.
Hour Angle
—°
At mean noon this won't be exactly 0°. Positive = sun still east of your meridian. Shows the Equation of Time (up to ±16 minutes).
GMST
—°
Same for everyone on Earth at a given moment. Independent of your location.