Monday, April 21, 2008

Mercury, Wednesday

Mercury just passed superior conjunction on April 16, but in the days to come it will bolt out to become easily visible low in the west-northwest at dusk. On Wednesday evening, April 23, Mercury should be visible within about 30 minutes after sunset if your sky is quite clear. Mercury will be shining at magnitude �1.6, slightly brighter than Sirius (the brightest of all stars). In fact, at that particular hour of the day, Mercury will be the brightest object in the sky!

So, if your sky is free of any horizon haze and there are no tall obstructions to your view (like trees or buildings) you should have no trouble in seeing it as a very bright "star" shining with just a trace of a yellowish-orange tinge. By April 30, Mercury will be setting as late as 85 minutes after the Sun. That evening, binoculars may show the Pleiades star cluster 4 degrees directly above it. (Your clenched fist held at arm's length measures about 10 degrees in width.)

In the evenings that follow, Mercury will slowly diminish in brightness, but it will also slowly gain altitude as it gradually moves away from the vicinity of the Sun. This is just the start of Mercury's best apparition of the year for mid-northern viewers. On the evening of May 6, be sure to look for a delicately thin sliver of a 1.5-day old crescent Moon sitting just a couple of degrees above and slightly to Mercury's right.


Much more.

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