Mariners Sighting

Date: 1550
Owner: Granger Collection, The
Source Type: Images


Navigating in the open ocean is practically impossible without the use of instruments, making them all important to controlling an overseas empire. Technologies for determining latitude, such as the astrolabe pictured in this sixteenth century drawing, had been used in the Middle East for centuries and were introduced to Iberia through texts and Moorish experts. Yet the rapid expansion of oceanic travel during the fifteenth and sixteenth centuries demonstrated the shortcomings of older instruments to Iberian navigators, captains, and pilots. The empirically observed challenges of actually arriving where one hoped to go prompted innovators and institutions to develop more advanced versions of navigational tools. In Spain, the Crown employed a salaried Master of Instruments to fabricate reliable and standardized navigational tools. Standardization allowed instructors at Seville's Casa de Contratacion to teach pilots how to use technology to gather and record measurements, information that would also be standardized (and thus universally applicable) by virtue of the tools.

The navigator pictured on the left is using an astrolabe to determine the ship's latitude, a calculation that relied on accurately measuring the degrees of arc separating the noontime sun from the horizon. The backstaff, as shown on this picture's right, was meant to perform a similar measurement, but was used with one's back to the sun (hence the name backstaff). The backstaff measured the degrees between the horizon and the sun by using the shadow cast onto the long end of the instrument, a method of observing the sun that was far easier on the eyes than attempting to take the measurement by staring directly at the sun, as one was required to do with an astrolabe or quadrant. Such practical inventions were the product of real problems encountered at sea, a clear example of the empirical approach to knowledge and innovation put to use.

CITATION: "Mariners Sighting." 16th C. The Granger Collection, New York. 0010693.