Ely Astronomy Club members gathered by the cannon on the green outside Ely Cathedral to watch as the smallest planet in the solar system travelled between the sun and the earth.
Clear skies and sunshine helped sky watchers to view the transit of Mercury across the surface of the air.
Ely Astronomy Club vice chair Alex Simpson said: “In the Seventeenth to Nineteenth Century, transits of planets like Mercury were used to measure the dimension of the solar system.”
A transit of Mercury typically occurs eight to 10 times a century, he said.
“1973 was the last time in which it would have been favorably viewed from the British Isles. I was at my late father’s house in North London. We hoped that we would be able to see it but it poured with rain.”
Mr Simpson added: “Sometimes a transit of Mercury can be seen from the Arctic, Antartica or a tiny little island in the Pacific but it’s rare to see it from the British Isles.”
He did not advise viewing the sun straight from a telescope, as this could cause damage to eyes.