Mercury Spotting

Mercury is visible this week (Jan 27 - Feb 2, 2014), briefly in the west, at dusk. The link below shows you where to find it. Forecasts predict some cloudiness through the week, so I wouldn't wait until Friday to start looking.

http://www.skyandtelescope.com/observing/home/241696701.html

Mercury is about 40% of the distance from the Sun as we are. That makes it so that it stays within about 28 degrees* of the Sun - which keeps it invisible in the solar glare much of the time. You can see it when it approaches what astronomers call "maximum elongation" - the furthest angular separation an inner planet (Mercury or Venus) gets from the Sun.

Mercury orbits pretty fast, so we get about six of these per year, (three for dusk viewings, three for dawn viewings). However, the way Mercury's orbit is tilted relative to ours makes it so that in our middle latitudes usually only one dusk and one dawn elongation per year sends it above the sky glow and not just further along almost parallel to the horizon. Those ideal times are the closest maximum elongation to the spring equinox for a dusk viewing, and the closest maximum elongation to the fall equinox for a pre-dawn viewing, so if you're an early riser, November 1, 2014 may be your time to see it.

i. Superior Conjunction with Sun

ii. Maximum Eastern. elongation: "evening star" (Jan 31 2014 (best view this year), May 25 2014, Sep, 21, 2014)

iii Inferior Conjunction with Sun

iv. Maximum Western elongation: "morning star" (Mar 14 2014, Jul 12 2014, Nov 1 2014 (best view this year))

v. Superior Conjunction with Sun

(Diagrams by E. Moebius & J. Hollweg).

* 28 degrees is under the best of circumstances. Mercury's orbit is highly elliptical, so for some maximum elongations, the angle is less than 20 degrees.