May 2015

Mercury BEST Right Now!

Mercury...Best Viewing for 2015
The first two weeks of May this year (i.e. right now!) is the best time to spot Mercury in 2015. Look in the western sky after sunset (use the chart in SKY SIGHTS to guide you). Or just look for the only bright “star” 5 to 10 degrees above the western horizon around 9:30 pm DST. It is surprising how easily it pops into view once the sky darkens down a bit. In the first week of May, Mercury glides past the Pleiades, M45, as shown in the image below taken May 1 at 9:54 pm DST.

Image by J.Hlynialuk Canon 60Da, 6s exp. ISO 1250, f.l. = 285 mm, f/8. Mercury was just 3.5° above the horizon and less than that above the rooftops that were just below out of frame. The Pleiades were just a bit over 2° from the planet on May 1, 2015.

As the planet moves eastward towards its Greatest Eastern Elongation (May 7), it appears farther and farther from the horizon at the same time of night. It is 20 minutes of arc higher, which is not a lot but every bit helps. The general motion of the sky also reduces Mercury's elevation as it does for the other sky objects as well. (Note: this works to our advantage in the morning sky).

But get out soon because, after GEE, Mercury drops back towards the horizon fairly quickly. By May 29 or so, it passes between the Sun and Earth (inferior conjunction) and then makes an appearance in the morning sky. By the end of June, it reaches Greatest Elongation West and then starts back towards the Sun again. No wonder the ancients gave the god Mercury winged feet, he really moves!

by John Hlynialuk