The Treworgy Planetarium at Mystic Seaport offers daily programs to acquaint Museum visitors with the stars, planets, and constellations of the nighttime sky. These programs help visitors understand how mariners use the sun and stars to determine directions and position at sea. In addition, the Planetarium offers a variety of classes including coastal and celestial navigation and GPS workshops for both adults and youths. Learn more about the Planetarium’s courses below and check the calendar for current offerings.
Introductory Celestial Navigation
A two-day class in the basic principles of celestial navigation from a modern perspective designed especially for yachtsmen and recreational boaters, but also appropriate for anyone interested in a quick introduction to celestial navigation. Celestial navigation is the ultimate backup when the electronics fail, and it is a tradition that connects us with maritime history. Students will learn how to adjust and use sextants available on the market today. This class covers the classic, time-honored method of finding latitude by the noon sun, as well as finding longitude by observations of the sun before and after noon (including frequently neglected corrections for statistics and the motion of the observer). Weather permitting, students will be able to measure the sun’s altitude around noon (from a nearby shore location) to determine latitude and longitude. This is real navigation, not just a class “about” navigation. Fast and intense, students who complete this weekend class will have the basic celestial navigation skills to cross any ocean using the sun, a sextant, and a few other simple tools.
Requirements. good basic arithmetic skills, but nothing beyond addition and subtraction. A familiarity with the basic geometry of angles, including degrees and minutes of arc. A familiarity with 24-hour time (16:00 is 4:00 p.m.). A good understanding of latitude and longitude on the globe.
Celestial Navigation: Nineteenth-Century Methods
A two-day introductory class about the history and actual techniques of celestial navigation as it was practiced aboard American sailing vessels in the Age of Sail. Students will learn how celestial navigation was once done and how to apply these same methods today. Students will learn how to use and adjust sextants and octants, both historical instruments and their modern equivalents. The class covers the classic method of finding latitude by “noon sun.” We’ll also learn in detail the math of the “time sight” which was used to determine longitude from the 19th through the middle of the 20th century. Throughout, we will compare what we’re doing with actual logbook entries and calculations in the collections of Mystic Seaport. Weather permitting; students will have opportunities to make actual sextant observations. This is real navigation, not just a class “about” navigation. Fast and intense, students who complete this weekend class will have the basic celestial navigation skills to cross any ocean using the sun, a sextant, and a few other simple tools.
Requirements. good math skills and especially a familiarity with the basic geometry of angles, including degrees and minutes of arc. A familiarity with 24-hour time. A good understanding of latitude and longitude on the globe. Unlike our “easy introductory” class, this course offers a more historical and more mathematical approach to celestial navigation.
Intermediate Celestial Navigation: Star Sights and Lines of Position
An excellent sequel to our Easy Introductory Celestial Navigation class. In this class, students will learn more about the use of the sextant and will learn the traditional “twilight round” of star sights for determining a vessel’s position by plotting lines of position and working with “H.O. 249” sight reduction tables. Students will also learn traditional shortcuts for locating the brighter navigational stars under the Treworgy Planetarium dome. Students will be provided with the necessary plotting tools and digital copies of the sight reduction tables.
Requirements. an introductory course or equivalent in the use of a sextant and other basic techniques in celestial navigation.
Direction by Magnetic Compass
This day-long workshop will teach the student to understand the earth’s magnetic field and its influence on the compass; determine magnetic variation and deviation; switch among true, magnetic, and “compass” directions; prepare and use a Deviation Card; and will provide basic instructions for adjusting the ship’s compass.