Table of Contents



Pre-Class Prep

Class 1
Class 2
Class 3
Class 4
Class 5
Class 6
Class 7
Class 8
Class 9
Class 10

>>Topical Articles<<
Assumed Longitude
Casio fx-260 Solar II
Emergency Navigation
Making a Kamal
Noon Sight
Pub. 249 Vol. 1
Sextant Adjustment
Sextant Skills
Sight Averaging
Sight Planning,
  Error Ellipses,
  & Cocked Hats
Slide Rules
Standard Terminology
Star Chart
The Raft Book
Worksheet Logic

Class 1:  July 11, 2019

Class Plan

  • Sometimes we lose audio.  Best strategy:  Both of us disconnect and reconnect.

    I cannot hear you.
  • Any questions before we begin.
  • Key concepts:
    • Geographic Point (GP) - spot where the celestial object is directly overhead
    • Greenwich Hour Angle (GHA) - equivalent to longitude, but measures always west, from 0° to 359°
    • Dead Reckoning (DR) - my best guess as to where I am
    • Assumed Position (AP) - a slightly tweaked version of the DR...tweaked to make calculating our fix easier.
    • Fix - where our celestial sights say we are
    • Circle of position (COP) - an enormous circle on the face of the earth, along which all sextant sights will be the same.
      • Take a single sight, and you know you are somewhere along the COP, but you don't know where.
      • Take sights on two celestial objects, and where the COPs cross is where you are.
        • The COPs will cross at two points, but if one crossing point is in Canada, the other is likely off the coast of it is difficult to get confused.
    • Viewed on a chart that is only 200 miles wide, the COP looks like a straight line...a line of position (LOP).
      • In celestial navigation, COP and LOP are used interchangeably.
  • Review how to read a drum micrometer scale.
  • Marcq St. Hilare - 1875:  "the Intercept Method" - uses an AP rather than direct calculation based on the DR.
  • If you have not already done so, please download and print:
  • If you don't yet have the class materials in your hand, you may download these:


Homework Assignment

  • Reading assignment in textbook: Introduction, Chapter 1, Chapter 2