Table of Contents
Casio fx-260 Solar II
Making a Kamal
Pub. 249 Vol. 1
& Cocked Hats
The Raft Book
Class 1: July 11, 2019
- Sometimes we lose audio. Best strategy:
Both of us disconnect and reconnect.
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
- Fix - where our celestial sights say we
- 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 Chile...so 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
- 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
- Reading assignment in textbook: Introduction, Chapter 1, Chapter 2