Mercury transit coming up!

Next Monday, Mercury will transit the Sun as viewed from Earth.  It’s quite hard to see — just a speck, really, but even with a modest telescope (properly filtered!) it is very clearly a disk, and you can tell over time that it is in motion.   Mercury is far enough away from Earth that unlike a solar eclipse (which is basically the Moon transiting the Sun), this will happen at almost precisely the same time everywhere.  Well, everywhere in daylight, anyway.  The charts below (given in universal time) will let you figure out when to look, and whether or not your part of the Earth will see it.  😉  Because a Mercury transit takes many hours, at least some part of the event will be visible from almost everywhere on Earth.  The exceptions are Australia, New Zealand, Indonesia, Papua New Guinea, various other south Pacific nations, the eastern part of southeast Asia and China, the Korean peninsula, Japan, and portions of eastern Siberia.  (Kamchatka will be able to see it, though.)

To view it, you will need some sort of solar observing setup.  Since Mercury is so tiny, magnification of at least 50x is recommended.  I will be using my 130mm Newtonian, with a full-aperture solar filter.  This is very important!  If using telescope or binoculars, you must put your filter over the front aperture, or focused sunlight may be hot enough to loosen your lenses and damage your telescope’s optics!  I used my Newtonian for the last Mercury transit, and it was effective.  Projection setups can work as well, but need to be able to focus very clearly for Mercury to be visible, and pinhole projectors are unlikely to be effective due to the small size.  The Sun does not have any particularly impressive sunspots right now (just some very small ones), so Mercury should be relatively easy to spot with sufficient magnification.

Otherwise, check the Internet during and after — people are bound to post pictures!

tm2016-Fig01b

tm2016-Fig02b

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