E. T. Fox, Historian

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Navigation Instruments

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 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 sun.

Back-staff and Almucantar staff Back-staff 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 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 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.

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