Cristina Zangelmi

That’s the day Galileo published the Sidereus Nuncius (Starry Messenger), starting one of the most important scientific revolutions in the history of humankind.

The historical dome of the Brera Astronomical Observatory houses the refracting telescope used by Schiaparelli to observe Mars, and from which sprang the controversy over the nature of the mysterious “canals”.

It’s very likely that even the astronomers in Ancient Greece, like Hipparchus of Nicaea, had occasionally noticed Uranus in their skies, because it is visible to the naked eye in excellent seeing conditions, but they thought it was a star.

By the end of the 18th century spider web strands were commonly employed for the reticles of astronomical instruments called filar micrometers. These instruments were used to determine positions, angular sizes and distances of the celestial objects observed with telescopes (the angular size of an object is its apparent size, as it appears from a given point of view, measured in fractions of a degree).