Astronomers use astrolabes for dozens of astronomical operations including telling time by the Sun or stars and determining the positions of planets.
This introduction to the astrolabe contains a striking, full-size, detailed design for an astrolabe, representing both the climate and the rete in fold-out plates.
Lansbergen, a Dutch Calvinist theologian, pastor, mathematician and astronomer, is perhaps best known for his astronomical tables published in 1632, the year of his death. He also published in 1620 (Dutch) and in 1630 (Latin) a popular work promoting the heliocentric system and refuting objections based on biblical interpretations. The frontispiece of his collected works (1663) displays a diagram of the Earth revolving around the Sun alongside portraits of celebrated astronomers including Copernicus and Tycho Brahe.
Lansbergen responded to Tycho’s argument about star sizes (explained in the gallery on the Controversy over the Comets). Tycho argued that if the Copernican system were true, one must accept the implication that stars are unlike the Sun, for even an ordinary star would be the size of the Earth’s orbit, and bright stars would be as large as the dimensions for Tycho’s entire universe. Lansbergen agreed, pointing to the vast sizes of stars as an expression of divine omnipotence and wisdom.