During this time period, European explorers used another bit of rather ancient technology: the astrolabe. The first astrolabes were actually made by the ancient Greeks for astronomy. They were later perfected by the Muslims in the Islamic golden age, and diversified by Persian astronomer Al-Sufi, where we can first trace the lineage of the astrolabe as a nautical navigation instrument. Just like the lateen sail, Europeans assimilated the astrolabe, which was the navigational instrument that guided Columbus to the Americas, and Magellan around the whole world. Unfortunately, since exact time was a key element to measuring latitude with an astrolabe, the accuracy of these tools was limited, because no clock could remain accurate over the long duration of the voyages.
Mid 16th century astrolabe. One person would hold the instrument by the upper loop, while another would operate the device