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world at mid-northern latitudes (with binoculars) above the eastern horizon some 40 minutes before sunrise. In stark contrast, you're likely to catch Mercury as much as two hours before sunrise (with the unaided eye) at temperate latitudes in the Southern Hemisphere.
• If you do spot Mercury near the moon tomorrow morning, be sure to notice the moon itself and earthshine on the waning crescent. Earthshine is that glow on the darkened portion of the moon. It's really light from Earth reflected back from the moon.
• Why is Mercury easier to see from Earth's Southern Hemisphere? Mercury has three greatest morning elongations in 2013: March 31, July 30 and November 18. Although the recent March 31 morning elongation - with Mercury at 28o west of the sun - ranks as the largest of them all, this is a poor morning apparition for the Northern Hemisphere. The late July showing will be more favorable for the Northern Hemisphere, despite Mercury swinging only 20o west of the sun on July 30, 2013. Although Mercury still resides a whopping 26o west of the sun right now, the advantage goes almost exclusively to the Southern Hemisphere.
• In either the Northern or the Southern Hemisphere, an inferior planet - a planet orbiting the sun inside of Earth's orbit - appears highest up in the morning sky when its greatest western elongation happens in late summer or early autumn. Since it's now early autumn in the Southern Hemisphere, this is a particularly good morning apparition of Mercury at southerly latitudes. And since it's early spring in the Northern Hemisphere, this is a particularly poor morning showing of Mercury in our part of the world.
• The ecliptic - the pathway of the moon and planets - intersects the horizon at a steep angle on early autumn mornings but at a shallow angle on spring mornings. Hence, tomorrow morning's showing of the moon and Mercury will be easier to see from the Southern Hemisphere by leaps and bounds!
• Bottom line: In early April, at mid-northern latitudes, Mercury rises less than one hour before the sun, yet at middle latitudes in the Southern Hemisphere, Mercury rises over two hours before the sun. Whether you live north or south of the equator, seek the waning crescent moon and Mercury in the east before sunrise on April 8, 2013. You might spot it!
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