Johann Werner's main work was on astronomy, mathematics and geography. In astronomy he followed Regiomontanus and was a skilled maker of instruments. A skilled observer, he recorded a comet on 1 June 1500 and kept a record of observations until 24 June 1500.
Werner's most famous work on astronomy and geography is In Hoc Opere Haec Cotinentur Moua Translatio Primi Libri Geographicae Cl'Ptolomaei written in 1514. This book contains a description of an instrument with an angular scale on a staff from which degrees could be read off. It also gives a method to determine longitude based on eclipses of the Moon.
In mathematics Werner worked on spherical trigonometry and conic sections. He was the first to use the formula
2sin(a)sin(b) = cos(a - b) - cos(a + b)
as an aid to calculation. This was used by Rheticus and Brahe and others up to the invention of logarithms.