|Sky and Telescope Magazine Diagram|
For the rest of Europe, Africa, and most of Asia, the transit also begins in the daytime but will still be underway when the Sun sets. Observers in Australia and eastern Asia will just have to watch online as it will not be visible to those parts of the globe. For more detailed information on of the Mercury transit, please visit Sky and Telescope's article covering the event.
Mercury is the smallest planet, therefore, you'll need a telescope to observe its transit. The black silhouette will appear only 12 arcseconds wide even though Mercury is at inferior conjunction. That’s about 1⁄160 of the Sun’s width and only a fifth the diameter (and 4% of the area) of Venus’s dramatic black disk during the rare transits of Venus. When first viewing, you might mistake Mercury for a small sunspot. It’s precisely round and lacks a gray penumbra. As Mercury travels across the Sun’s vast expanse, how readily can you see its motion? If it passes near a sunspot, can you see that it’s darker than even the sunspot’s umbra? When Mercury departs at egress, the sequence of phenomena at ingress unwinds in reverse order.
|Image from In-The-Sky.org|
Sources: Sky and Telescope Magazine, NakedEyePlanets.com