Little is known of Keyser's life outside of his astronomical observations and East Indies voyages. After making several voyages under the Portuguese flag, including one to Brazil, Keyser participated as the chief navigator and head of the steersmen for the first Dutch voyage to the
East Indies (the "
Eerste Schipvaart"), which left
Texel with four ships on 2 April 1595 under
Cornelis de Houtman. He had been trained by cartographer
Petrus Plancius in mathematics and astronomy. Plancius, a key promoter to the Dutch East Indies expeditions, had instructed Keyser to map the skies in the
southern hemisphere, which were largely uncharted at the time. When the fleet finally was able to obtain fresh supplies at
Madagascar on 13 September 71 of the 248 sailors had died, most of
scurvy. The surviving crew stayed for several months on the island, to recover and make repairs, at which point Keyser probably made most of his celestial observations. He was aided in this by
Frederick de Houtman and Vechter Willemsz. After leaving Madagascar, it took another four months (February to June 1596) for the ships to reach
Sumatra and finally
Bantam on Java. Trade negotiations went sour, perhaps caused by Portuguese instigators, perhaps by inexperience, and the crew was forced to find drinking water and other supplies on Sumatra across the
Sunda Strait. Keyser died during this crossing on 13 September 1596. On 14 August 1597, 81 survivors including Frederick de Houtman made it back to Texel. All the scientific observations gathered on the voyage were turned over to Petrus Plancius. ==Constellations==