Ruđer Josip Bošković was a physicist, astronomer, mathematician, philosopher, diplomat, poet, theologian and Jesuit priest, who lived between 1711 and 1787. He was born in Dubrovnik. He lived most of his life in Italy and France, but he also spent time in other parts of Europe, including the Romanian territories.

In 1756 he began a long career as a diplomat. He spent the winter 1761-62 in Constantinopolis, the Ottoman capital. He then moved to Poland, after crossing Bulgaria, Dobruja and Moldova.

More information about his journey through the Romanian territories can be found in the Giornale di un viaggio da Constantinopoli in Polonia published in 1762. This is a 323-page book that contains a detailed description of the journey, which started on the 24th of May 1762 and finished on the 15th of July of the same year.

On the 23rd of June he arrived at Galaţi in Moldavia, the largest port town on the Danube River. The unending rain forced travellers to spend a few days there. Boscovich, the astronomer, took advantage to carry out astronomical measurements which are now of greatest importance to Romanians. Indeed, they were the first measurements of which we know for sure the author, the method and the instrument.

After more calculations, he established for Galaţi a latitude of 45° 23', very close to the correct one, of 46°40'. In order to determine the longitude, Boscovich measured various distances between Sun and Moon after having set a clock that counted the seconds by means of the Sun’s height determined thanks to its reflection on the water.

A few days later, Boscovich left Galaţi and arrived at Iassy on the 3rd of July. During the journey he met M. De la Roche, secretary to the Prince of Moldavia. Near the palace there was the beautiful lake the astronomer used for determining the coordinates of the location. On the 6th of July he established the latitude of 47° 9'; the centre of Iassy was almost one minute ahead of the Prince’s residence, that is, 47° 10', which is a very accurate figure. But two observations of the Moon at its passage at the meridian gave him a different result: 47° 12', which Boscovich considered to be closer to reality, since this time he observed the Moon both directly and through its reflection on the lake.

He used a three-foot telescope designed by the famous English optician John Dollond, with a double objective made of two different types of glass. At its end, he could mount an instrument containing a small, mobile metal mirror, which Boscovich built in London. It helped to project the image of the Sun onto a wall in a camera obscura for the observation of sunspots and eclipses.

This presentation will consider in more detail his rich astronomical calculations and will also give a flavour of his colourful descriptions of the places he visited.