February 4th, 2013 by James Ayre
The middle of February is going to be the best time of year for amateur astronomers to observe the planet Mercury in 2013. Mercury will be shining brightly, and be especially easy to see, during the evenings of February 11-21, when it will hang around for an hour or so after sunset.
At the same time, the planet Mars will also close by, nearly in conjunction with Mercury. They will be at their closest from February 7th to 8th.
They will both be easily visible with the naked eye, so long as you have an uninstructed view of the western horizon. Of course, with binoculars, or a camera, they will be much easier to see.
“A half hour after sunset, start scanning the horizon where the Sun’s glow is strongest. Mercury should already be visible as a faint pinprick of light through binoculars, and it’s likely to become more prominent as the sky grows darker.”
There will also be a very thin crescent Moon visible to the lower right of those two starting on the 10th.
Some general information on observing Mercury:
“Mercury’s apparent magnitude varies between −2.6 (brighter than the brightest star Sirius) and about +5.7 (approximating the theoretical limit of naked-eye visibility). The extremes occur when Mercury is close to the Sun in the sky. Observation of Mercury is complicated by its proximity to the Sun, as it is lost in the Sun’s glare for much of the time. Mercury can be observed for only a brief period during either morning or evening twilight.”
“Mercury can, like several other planets and the brightest stars, be seen during a total solar eclipse.”
“Like the Moon and Venus, Mercury exhibits phases as seen from Earth. It is ‘new’ at inferior conjunction and ‘full’ at superior conjunction. The planet is rendered invisible from Earth on both of these occasions because of its relative nearness to the Sun.”
“Mercury is technically brightest as seen from Earth when it is at a full phase. Although the planet is farthest away from Earth when it is full the greater illuminated area that is visible and the opposition brightness surge more than compensates for the distance. The opposite is true for Venus, which appears brightest when it is a crescent, because it is much closer to Earth than when gibbous.”
“At tropical and subtropical latitudes, Mercury is more easily seen than at higher latitudes. This is the result of two effects: (i) the Sun ascends above the horizon more steeply at sunrise and descends more steeply at sunset, so the twilight period is shorter, and (ii) at the right times of year, the ecliptic intersects the horizon at a very steep angle, meaning that Mercury can be relatively high (altitude up to 28°) in a fully dark sky. Such conditions can exist, for instance, after sunset near the Spring Equinox, in March/April for the southern USA and in September/October for South Africa and Australasia. Conversely, pre-sunrise viewing is easiest near the Autumn Equinox.”
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