A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Ed Popko
Date: 2015 Oct 5, 05:20 -0700
Frank adds another notch to the handle of his sextant with last weekend's great workshop "Celestial Navigation 19th Century Methods" at Mystic Seaport (October 3-4, 2015).
An excellent turnout followed Frank’s overview of 19th century LAN and Time Sights. His examples were taken from whaling ship logs and snippets from Cook's voyages. Reproductions of actual hand written calculations are deciphered and Frank steps through their calculations with the aid of a perpetual almanac and recreated period log tables.
There is no better way to understand celestial navigation as it’s actually practiced than to place yourself in their shoes, see a day's work, follow their calculations and appreciate their shortcuts such as the Navigator's Right Triangle (and it's not 90 degrees). It's quite satisfying to play historic cryptographer, decipher number patterns, and spot familiar calculation sequences. You appreciate these navigator’s methods, their practical limits and some surprising level of accuracy.
This workshop offered many extras as well.
At Saturday’s class, Frank conducted a brief session in the Treworgy Planetarium. He demonstrated techniques for identifying navigation stars and used the projection system to demonstrate altitude, declination, GHA, relation of latitude to celestial equator (rise/set angles of stars) and Polaris' eccentric movement about the celestial North Pole.
After Saturday's class, we were fortunate enough to have a guided tour of “The Quest for Longitude - Ships, Clocks & Stars" exhibit. This amazing exhibit, on loan from the National Maritime Museum in London, features early cross staffs, back staff and functioning reproductions of John Harrison's wood clocks and his amazing H1, H2, H3 and H4 series chronometers. If you have never seen Harrison's work in person, you are missing a lot. These are more than chronometers; they are works of art with amazing engraving and filigree. Harrison’s innovations include the Fusee (a cone/chain device that equalizes the uneven pull of the mainspring on the clock gears as the spring runs down), spring detent escapement and balance wheel. Side exhibits explain how they work and show Cook’s tests validated K1 (Larcum Kendall’s reproduction of Harrison’s H4). Another exhibit shows John Bird's 1758 sextant prototype developed with Captain John Campbell who suggested its design and tested it with Mayer's lunar tables. It’s shocking to see how little this design has changed in 250 years.
The weather on Sunday gave attendees another lucky break. The class was able to go to Avery Point, University of Connecticut campus. Loaner sextants from the Seaport’s Susan P. Howell Library collection gave everyone a chance to take shots. Frank’s demonstrated useful sextant handling techniques and ways to improve sight accuracy.
All in all, a great workshop. A credit to both Frank and the wonderful atmosphere provided by Mystic Seaport.