He was a native of Denmark.

His whole life may be said to have been devoted to astronomy.

A small work that he published when a young man brought him under the notice of the King of Denmark, with whose assistance he constructed, on the small island of Hulln, a few miles north of Copenhagen, the celebrated Observatory of Uranienburg.

Here, seated in "the ancient chair" referred to in the text, and surrounded by numerous assistants, he directed for seventeen years a series of observations, that have been found extremely accurate and useful.

On the death of his patron he retired to Prague in Bohemia, where he was employed by Rodolph II.