Fact Sheet
Elongations and Conjunctions
A planet's "elongation" refers to how far it is separated from the Sun in the sky, as viewed from Earth. At "greatest elongation," the planet has reached its maximum separation from the Sun. This is the best time to view Mercury because it's the farthest away from the Sun's glare. When a planet's elongation is zero, it is aligned with the Sun and Earth, and is in a "conjunction." Because their orbits lie inside Earth's, Mercury and Venus can have both "inferior conjunctions," when they are between the Sun and Earth, and "superior conjunctions," when they lie on the other side of the Sun from Earth.
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