Elongation is a term that refers to the angle between the Sun and a planet as viewed from Earth. The best
times to observe an inferior planet (Venus and Mercury which orbit the Sun inside the Earth’s orbit), is when they are close to greatest elongation. They
are always seen as morning objects (near western elongation) or evening objects (near eastern elongation). Venus has a maximum elongation of 47º and
Mercury 28º.
2007
Greatest elongations for the inferior planets this year:
Mercury western: March 22nd – at 28º not visible as below the horizon.
July 20th – at 20º rising 1.5 hours before the Sun.
November 8th – at 19º and –0.5 magnitude, rising 2 hours before the Sun.
Mercury eastern: February 7th – at 18º and –0.5 magnitude.
June 2nd – at 23º and 0.6 magnitude.
September 29th – at 26º but too low in the sky for observation.
Venus western: October 28th – at 46º and –4.4 magnitude, rising about 4 hours before the Sun.
Venus eastern: June 9th – at 46º and –4.3 magnitude, setting just over 2 hours after the Sun.
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