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As an adjunct to his work as an historian Ed Fox is also a noted maker of replica navigation instruments from the pre-sextant age. With a careful and meticulous attention to detail, Ed’s instruments are made as faithfully as possible to the original designs, and are every bit as accurate as those available to mariners in the age of sail. Ed has made instruments for sailors, museums, and historical reenactors, as well as for his own collection, and has tested several of them at sea, with encouraging results.
Cross-staff. The origins of the cross-staff are lost in the mist of time, but it was
certainly in use by the fifteenth century. Used to measure the angle of the sun, the
cross-staff is accurate to 1 degree, but requires the navigator to look directly towards the
Back-staff and Almucantar staff. The concept of the back staff, which uses
shadows to eliminate the need to look at the sun, was devised by Devon seaman John Davis in the
early 1590s, and was steadily developed over the seventeenth century. The most complex examples
of the instrument bore a scale capable of providing readings accurate to 5 minutes (1/12 of a
degree), and, thanks to its simple and robust nature, remained popular even after the
introduction of the sextant in the mid-eighteenth century.
The almucantar staff works in the same was as the back-staff, but is a considerably more compact instrument, used for measuring the angle ofthe sun at very low altitudes.
Gunter quadrant. The simple quadrant was in use from ancient times to measure angles,
but innovations by Edmund Gunter in the seventeenth century allowed for much more complex
operations, such as determining the sun’s maximum declination for any given day of the
year, and finding the time much more reliably than a sundial.
Nocturnal. Not a navigation instrument per se, the nocturnal’s prime function
was to find the time at night by the position of stars in relation to Polaris. Later examples
often featured scales for latitude correction.
All instruments can be made to order, and Ed is always looking for interesting new projects to undertake. Ed is also available to demonstrate the use of the instruments. Please contact for details.This website created and maintained by Exploit The Web Ltd © 2011