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physical phenomena > event > celestial event > periodic celestial event > location dependent periodic celestial event > astronomical horizon event

astronomical horizon event
subject			fact

astronomical horizon event	has definition The time and azimuth at which a celestial body crosses the astronomical horizon of an oberver.
	is a kind of location dependent periodic celestial event
location dependent periodic celestial event	has observer location
periodic celestial event	has period
event	has duration
	has synonym world point
	has time of occurrence

Kinds of astronomical horizon event :

• moonrise (3 facts) - The time at which the apparent upper limb of the Moon is on the astronomical horizon just before it rises; i.e., when the true zenith distance, referred to the center of the Earth, of the central point of the disk is 90°34' + s - π, where s is the Moon's semidiameter, π is the horizontal parallax, and 34' is the adopted value of horizontal refraction.
• moonset (3 facts) - The times at which the apparent upper limb of the Moon is on the astronomical horizon just as it sets; i.e., when the true zenith distance, referred to the center of the Earth, of the central point of the disk is 90°34' + s - π, where s is the Moon's semidiameter, π is the horizontal parallax, and 34' is the adopted value of horizontal refraction.
• sunrise (3 facts) - The times at which the apparent upper limb of the Sun is on the astronomical horizon; i.e., when the true zenith distance, referred to the center of the Earth, of the central point of the disk is 90°50', based on adopted values of 34' for horizontal refraction and 16' for the Sun's semidiameter.
• sunset (3 facts) - The times at which the apparent upper limb of the Sun is on the astronomical horizon; i.e., when the true zenith distance, referred to the center of the Earth, of the central point of the disk is 90°50', based on adopted values of 34' for horizontal refraction and 16' for the Sun's semidiameter.