The online class "Lunars: Finding Longitude by Lunar Distance" was a very interesting introduction to the esoteric history of lunars as practiced at sea in the pre chronometer 18th century tall ship era. Practical instruction was also done demonstrating the physical process of observing a lunar with a sextant followed by a how to lunar sight reduction example using a pocket calculator, formulae, and tables. A very rewarding experience.
Greg Rudzinski
Retired Merchant Mariner
SUNY Maritime class of 80
Longitude by Lunars
"Lunar Distances" or lunars for short were used to determine longitude at sea in the period from about 1767 until 1850 (and rarely after that date). This was a time when chronometers were not yet widely available at a reasonable price and were considered unreliable on long voyages. The principle behind lunars is simple. The Moon in the sky is the hour hand of a great clock. The stars along its path are the numbers on the face of the clock. If we can measure the Moon's position relative to the stars, we can read the time from the clock. Comparing that absolute time with local time, usually determined by a time sight, we have our longitude. A one hour difference in time corresponds to a 15 degree difference in longitude.-
Predicted Lunars (UPDATED)
Traditionally, lunar distances could be used for navigation only if a navigator had access to predicted distances. These were published in almanacs around the world from the late 18th through the early 20th centuries. Today the predicted distances are no longer published, but they can be calculated without much difficulty. The predictions generated by this web site are extremely accurate. They are the most accurate available today. The time period covered is 1750 to 2050 so the predictions here can be used for modern lunars or for analysis of historical lunar observations. -
Clear a Lunar (UPDATED)
This web-based app will analyze a lunar observation and generate your longitude in a fraction of a second. Historically, the analysis of lunars required about twenty minutes of work and a table of logarithms. Even if you decide to work a lunar by hand with pencil and paper, this online calculator will allow you to check your results. Originally developed and made available online in the summer of 2004, this app has been field-tested by myself and other navigation enthusiasts thousands of times. Its results are accurate to approximately one second of arc. -
Online Nautical Almanac (UPDATED)
A complete source for Nautical Almanac ephemeris data covering the period 1750 to 2050. The positions of the Sun, Moon, navigational planets and stars are generated for every hour of the day at a high level of accuracy just as in the published almanacs. This online app permits customization of display options so that data are generated that are relevant for your location and interests. -
Easy Lunars
An account of a simple technique for analyzing lunars using nothing more than the basic corrections and data in the Nautical Almanac and a handheld calculator. Lunars are not difficult. They take a little practice, and you may have to re-familiarize yourself with the use of a calculator, but any navigator can enjoy the challenge and experience of this historical method of navigation.
Comments:
Greg Rudzinski wrote: 6👍
Jeffrey Rock wrote: 8👍
Lunar Distance and Age of Sail Classes:
Fascinating classes taught by a fascinating and capable instructor.
Lunars class is challenging and fun. Frank presents several different recipes for accomplishing lunars, one of which seems almost easy (kind of). Highly recommended for anyone interested in celestial navigation or nautical navigation history.
Jeffrey Rock
FAA Designated Pilot Examiner
Fascinating classes taught by a fascinating and capable instructor.
Lunars class is challenging and fun. Frank presents several different recipes for accomplishing lunars, one of which seems almost easy (kind of). Highly recommended for anyone interested in celestial navigation or nautical navigation history.
Jeffrey Rock
FAA Designated Pilot Examiner
Mark Coady wrote: 11👍
I have now done every course I think that has been offered so far at Mystic Seaport taught by Frank Reed in the last two years. I found the courses to all be extremely rewarding.
Several things stand out. The course material is presented in a balanced way, with a well thought mixture of detailed calculation, broken up by historical, factual, and hands-on aspects. This type of teaching is well suited to most, as it provides periods of more intense reasoning with relaxation and humor. Anyone can walk away with new-found knowledge. I also feel that the approach of understanding historical context and a simple practical approach is unique. It has gone a great way toward clearing up a lot of my preconceived ideas and confusions resulting from the many contradictory or esoteric approaches found in various volumes or on the internet.
Very simply, I learned a lot and it went a long way toward clearing up a mess. I was fascinated the whole time. The courses and NavList provide the tools to keep learning even after the course is over. I left able to measure what I see with a more calibrated eye for real world application, and a greater appreciation of human history. I can strongly recommend these classes for the curious, the fascinated, the historian, the hardcore navigator, or the armchair one. There is something in them for all.
I also found the NavList community to be helpful and encouraging as my journey continues. I hope I can undertake even more material in additional courses in the future.
"There is nothing - absolutely nothing - half so much worth doing as simply messing about in boats" (Kenneth Grahame, from the "Wind in the Willows")
Capt. Mark
Several things stand out. The course material is presented in a balanced way, with a well thought mixture of detailed calculation, broken up by historical, factual, and hands-on aspects. This type of teaching is well suited to most, as it provides periods of more intense reasoning with relaxation and humor. Anyone can walk away with new-found knowledge. I also feel that the approach of understanding historical context and a simple practical approach is unique. It has gone a great way toward clearing up a lot of my preconceived ideas and confusions resulting from the many contradictory or esoteric approaches found in various volumes or on the internet.
Very simply, I learned a lot and it went a long way toward clearing up a mess. I was fascinated the whole time. The courses and NavList provide the tools to keep learning even after the course is over. I left able to measure what I see with a more calibrated eye for real world application, and a greater appreciation of human history. I can strongly recommend these classes for the curious, the fascinated, the historian, the hardcore navigator, or the armchair one. There is something in them for all.
I also found the NavList community to be helpful and encouraging as my journey continues. I hope I can undertake even more material in additional courses in the future.
"There is nothing - absolutely nothing - half so much worth doing as simply messing about in boats" (Kenneth Grahame, from the "Wind in the Willows")
Capt. Mark
