As we prepare for the Transit of Mercury here at the Royal Observatory our curator, Louise Devoy, looks back to observations made here in 1753.

Astronomical Observations, made at the Royal Observatory at Greenwich, from the year 1750 to the year 1762, volume 1 (RMG ID item: PBG0607/1)

Astronomical Observations, made at the Royal Observatory at Greenwich
As we turn our thoughts towards Mercury and the forthcoming transit on 9 May, here is a great example of how astronomers at the Royal Observatory, Greenwich, have observed this event over the past 300 years. The volume shown here is the compilation of observations made by the third Astronomer Royal, James Bradley (1692-1762), during his 20 year career at Greenwich. 
Astronomer Royal James Bradley at the Royal Observatory Greenwich
On 6 May 1753, shortly after dawn, he observed the last few hours of the transit of Mercury as the inner planet appeared to move across the face of the Sun. The inclination of Mercury’s orbit means that it usually appears above or below the Sun, as seen from Earth, but occasionally, all three celestial bodies lie in the same plane and the black disc of Mercury appears to cross the Sun’s disc over several hours. These transits occur in 3-year pairs approximately every 10 years; this means that the next one for us will be on 11 Nov 2019, followed by another set in the 2030s. 
Transit of Mercury observations at Royal Observatory Greenwich
For more details on how you can safely observe the transit here at Greenwich with our expert astronomers, visit our website
We'll also be sharing live pictures from our Great Equatorial Telescope on Twitter
Louise Devoy
Curator of the Royal Observatory Greenwich