Spot Mercury At Dawn

Mercury is always a difficult object to spot, always clinging closely to the suns apron strings. But you might be excused for missing its brief appearance this week in the dawn skies.

After many attempts to observe Mercury, Ive found that the best time to spot it is about half an hour before sunrise in the morning sky, or half an hour after sunset in the evening sky. Its always a balancing act between Mercurys low altitude and the brightness of the background sky. I find 7x50 or 10x50 binoculars helpful in spotting Mercury, though once Ive located Mercury in binoculars I usually have no trouble seeing it naked eye.

Unless youre paying close attention to the sky, youre likely to miss the current apparition of Mercury. In the northern hemisphere, Mercury can be seen half an hour before sunrise. Credit: Starry Night Software.

Because of the tilt of the ecliptic, the path the Sun and planets follow across the sky, some apparitions of Mercury are more favorable than others. Usually apparitions which are favorable for observers in the northern hemisphere are unfavorable for observers in the southern hemisphere, and vice versa.

The tilt of the ecliptic would indicate that this apparition favors southern observers, but as you can see from these two views, it really isnt much different: catching Mercury this week will be a challenge for observers everywhere in the world.

A secondary factor affecting Mercurys visibility is the tilt and eccentricity of its orbit. At 7 degrees, Mercurys tilt is greater than any other planet. The eccentricity of its orbit, which measures how far it deviates from a circle, is also the greatest, more than twice as eccentric as Mars orbit.

The tilt this week also favors southern observers, as you can see in the charts, where Mercurys orbit is marked in red and the ecliptic in green, but even this doesnt help much.

The view is not much better in the southern hemisphere. Credit: Starry Night software.

If you are successful in spotting Mercury in the next few days, congratulate yourself, and let us know here!