![]() The British Astronomical Association (BAA) has an excellent online guide to viewing the Sun safely. Furthermore, clouds can break in an instant and glimpsing the Sun - even for a fraction of a second - can cause instant and irreparable eye damage. At such times the Sun may seem to be of a safe intensity, but the telescope will still concentrate harmful infrared and ultraviolet light that will damage your eyesight. I make no apologies for repeating the warning to never look at the Sun through an unfiltered optical instrument, even when it is low in the sky or heavily obscured by mist or fog. To see Mercury in transit, one must use a binocular or a telescope. This means that, as seen through special eclipse sunglasses, Mercury will be too small to see with the protected naked eye.Ī caveat for binocular and telescope users Given Mercury’s diameter of 4879 kilometres (3032 miles), this means that the planet will appear as a jet black circular silhouette just 9.9 arcseconds across, or 1/196th of the Sun’s diameter. ![]() Most times Mercury passes above or below the Sun’s disc, but 13 or 14 times every century, in the months of May or November when the orbital planes of Earth and Mercury align, the innermost planet can be seen passing directly in front of our nearest star.Īlthough Mercury is at its closest to Earth at inferior conjunction, it still lies some 101 million kilometres (63 million miles) distant at the middle of this transit. Mercury makes one orbit of the Sun in just 88 days, but as seen from our moving vantage point on Earth the planet comes between us and the Sun (termed inferior conjunction) every 116 days, on average. Shortly after 12:35pm GMT on Monday, 11 November 2019, suitably equipped observers in the British Isles can witness the start of a 3.7-hour spectacle that hasn’t been seen for three-and-a-half years - the silhouette of innermost planet Mercury transiting the face of the Sun. Newtonian reflector users need to rotate the image 180°, while refractor, Schmidt- and Maksutov-Cassegrain telescope users with a star diagonal should mirror the view east-west. The view corresponds to an equatorially-mounted, erect-image telescope with a solar filter attached. For the period after sunset (~4:18pm GMT) in the UK, the corresponding time in New York and Universal Time is also shown. This looping movie shows a simulation of innermost planet Mercury’s journey across the face of the Sun on Monday, 11 November 2019 as seen by an observer in the heart of the British Isles.
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