Johan Maurits Mohr was a Dutch

Netherlands

The Netherlands is a constituent country of the Kingdom of the Netherlands, located mainly in North-West Europe and with several islands in the Caribbean. Mainland Netherlands borders the North Sea to the north and west, Belgium to the south, and Germany to the east, and shares maritime borders...

-German

Germany

Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...

 pastor

Pastor

The word pastor usually refers to an ordained leader of a Christian congregation. When used as an ecclesiastical styling or title, this role may be abbreviated to "Pr." or often "Ps"....

 who studied at Groningen University from 1733 and settled in Batavia

Jakarta

Jakarta is the capital and largest city of Indonesia. Officially known as the Special Capital Territory of Jakarta, it is located on the northwest coast of Java, has an area of , and a population of 9,580,000. Jakarta is the country's economic, cultural and political centre...

 (Dutch East Indies

Indonesia

Indonesia , officially the Republic of Indonesia , is a country in Southeast Asia and Oceania. Indonesia is an archipelago comprising approximately 13,000 islands. It has 33 provinces with over 238 million people, and is the world's fourth most populous country. Indonesia is a republic, with an...

) in 1737. Mohr's greatest passion was in astronomy

Astronomy

Astronomy is a natural science that deals with the study of celestial objects and phenomena that originate outside the atmosphere of Earth...

 but he was also keenly interested in meteorology

Meteorology

Meteorology is the interdisciplinary scientific study of the atmosphere. Studies in the field stretch back millennia, though significant progress in meteorology did not occur until the 18th century. The 19th century saw breakthroughs occur after observing networks developed across several countries...

 and in vulcanology.

In 1765 Mohr built a large private observatory that was equipped with the best astronomical instruments of his time. His observatory, which had cost him a small fortune, was visited and praised by Louis Antoine de Bougainville

Louis Antoine de Bougainville

Louis-Antoine, Comte de Bougainville was a French admiral and explorer. A contemporary of James Cook, he took part in the French and Indian War and the unsuccessful French attempt to defend Canada from Britain...

 and James Cook

James Cook

Captain James Cook, FRS, RN was a British explorer, navigator and cartographer who ultimately rose to the rank of captain in the Royal Navy...

.

Mohr observed the Venus transits

Transit of Venus

A transit of Venus across the Sun takes place when the planet Venus passes directly between the Sun and Earth, becoming visible against the solar disk. During a transit, Venus can be seen from Earth as a small black disk moving across the face of the Sun...

 of 6 June 1761 and 3 June 1769 and the Mercury transit

Transit of Mercury

A transit of Mercury across the Sun takes place when the planet Mercury comes between the Sun and the Earth, and Mercury is seen as a small black dot moving across the face of the Sun....

 of 10 November 1769. He also made meteorological observations and measurements of the magnetic declination

Magnetic declination

Magnetic declination is the angle between magnetic north and true north. The declination is positive when the magnetic north is east of true north. The term magnetic variation is a synonym, and is more often used in navigation...

 at Batavia.

After Mohr's death his observatory was damaged by an earthquake in 1780, fell into ruin and was demolished in 1812.

The minor planet 5494 Johanmohr is named in his honour.