In astronomy, contact is any of the four stages that mark the start or end of an eclipse, occultation, or transit. First contact is the instant when an eclipse, occultation, or transit begins. Second contact is the instant that totality begins in a total solar or total lunar eclipse. Third contact is the instant that totality ends. Fourth contact is the instant at which an eclipse, occultation, or transit ends.
Related category• CELESTIAL MECHANICS
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