Our guiding principle for this booklet was to provide a means of learning and executing a position fix at sea when a vessel has run out of power and all the batteries have been consumed, so there is no GPS available. We wanted a solution that is compact and inexpensive, using tables and procedures that are easy to learn and use. This goal led to our proposing a minimum kit that mariners would not hesitate to add to their gear to cover the unlikely situation it would actually be needed. Mariners who cross oceans in small boats realize they must be self-reliant and cover all contingencies.
For those who do not have the chance to learn the full range of celestial navigation before departure, this booklet and a Mark 3 sextant provide a minimum backup kit that can be used to navigate across any ocean if needed.
This book includes a 60-page Almanac of the sun to provide quick and easy solutions for Latitude and Longitude, as well as a unique new method for finding the corrections needed to find Latitude by Polaris, as well as in depth discussion of how to use a Mark 3 plastic sextant with emphasis on reading the angle scales.
Contents
1. OVERVIEW
2. SEXTANT SIGHTS WITH THE MARK 3 SEXTANT
Reading the Sextant Scales
Adjusting the Index Mirror
Index Mirror Adjustment Using Only a Sea Horizon
Index Mirror Adjustment with a Star
Index Mirror Adjustment with Cloud Edges
3. TAKING SUN SIGHTS
Aligning the Sun on the Horizon
4. A COOKBOOK APPROACH TO FINDING POSITION
Correcting the Sextant Height to get the Observed Height
Finding Latitude and Longitude From the Sun
The Recipe
Finding the Peak Height of the Sun
Finding the Time of LAN
Sailing Under the Sun
5. WORKED LAN EXAMPLES
Latitude Example 1
Easy LAN Rule
Longitude Example 1
Latitude Example 2
Longitude Example 2
6. LATITUDE BY POLARIS
Latitude by Polaris Example
7. PLOTTING POSITIONS AND DR TRACKS
Setting Up a Universal Plotting Sheet
Using the Plotting Sheet
Getting by Without Dividers
8. BACKGROUND INFORMATION
8.1 Timekeeping in Navigation
8.2 Lat, Lon, nmi, and DR
8.3 Adjusting the Index Mirror on Land
8.4 Predicting the Time of LAN From Your DR-Lon
8.5 Principles of the Noon Sight for Lat and Lon
8.6 Universal Rule for LAN
9. GPS BACKUP KIT--THEME AND VARIATIONS
10. REFERENCES
11. TABLES
Sun Almanac
Refraction Table, Dip Table, Polaris Table
Increments Table
David Burch is a Fellow of the Royal Institute of Navigation in London as well as a Fellow of the Institute of Navigation in Washington, DC, from which he received the Superior Achievement Award for outstanding performance as a practicing navigator. He has logged more than 70,000 miles at sea, including twelve transoceanic yacht races, with several first place victories and a passage record for boats under 36 feet that lasted 16 years. He also navigated the only American entry in the storm-ridden 1993 Sydney to Hobart Race. On the academic side, he is a former Fulbright Scholar with a PhD in physics. As Founding Director of Starpath School of Navigation in Seattle he has designed courses and taken part in the teaching of marine weather and navigation for more than 30 years. He continues to work on the development of online training materials, which are presented at starpath.com. His articles on special topics in navigation and weather appear at starpath.com/articles.
