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Transit of Mercury, 11 November 2019

A transit of Mercury across the Sun takes place when the planet Mercury passes directly between the Sun and a superior planet. Transits of Mercury with respect to Earth occur in May or November and about 13 or 14 times during the course of a century. Lasting several hours, Mercury appears during the transit period as a tiny black dot moving across the disk of the Sun. Here, observed from the UK, from 12:35pm GMT on 11th November 2019, such a transit was visible. A couple of photographs of this event are shown below (where Mercury is seen as a black dot to the right):

Taking the photographs was not an easy task insofar as due to cloud cover, the visibility of the Sun was poor and highly variable. Photographs were taken through a black polymer solar filter sheet placed over the end of a reflecting telescope (the end where light enters) and acquired with a digital camera eyepiece, computer and software (Celestron telescope model #21045, D=114mm, F=900mm; MikrOkular Full HD Microscope/Telescope Digital Camera #5913650, Bresser GmbH; Win 10 laptop; SharpCap 3.2 Astro Capture Software).

The next transit of Mercury will occur in 2032. Transits of Venus also occur, although these are much less frequent than those of Mercury, in part because Mercury is closer to the Sun and orbits it more rapidly; the next transit of Venus is due to happen in the year 2117.

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