NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Andrés Ruiz
Date: 2010 Jun 3, 08:03 +0200
Ocean Navigator - June 2010
Two articles from our friends John Karl and Greg
Rudzinski!!!
Celestial
Navigation
by David Berson
The
benefits of using H.O. 249 for Selected Stars
There is no greater
thrill for the evolving celestial navigator than in obtaining a fix from a star
sight. This is the navigational sine qua non and the goal to which navigators
aspire. The most difficult aspect of taking star sights — especially if
you are older than age 50 — is finding the stars, recording the time, and
getting a sextant altitude observation (Hs) in dim light. With or without
glasses it can still be a chore. The stars, it might be said, are for young
eyes, but with a good red-light flashlight and some practice the physical act
of shooting stars can be learned!
The easiest and most fool-proof method requires the use of
H.O. 249 Vol. 1, Selected Stars. This volume is published in 10-year editions
called epochs — the latest version having come out in 2010. The table is
laid out with latitude pages from 89° North to 89° South. The local hour angle
(LHA) of Aires for seven stars is listed from 0° to 359°. The seven stars have
been chosen for their magnitudes (brightness) and for their ability to give the
navigator good cuts — they are positioned about 45° relative to each
other. Continue reading…
About the Author:
Contributing Editor David Berson writes the Nav Problem page in every issue of Ocean Navigator.
He is also the owner and operator of Glory, an electrically
powered excursion boat, in
Questions or
comments for Dave? editors@oceannavigator.com
More Ocean Navigator articles:
The
sextant's compromising views
by John Karl
When it comes to celestial
navigation, a prime question from both experienced navigators and
celestial-navigator wannabes is this: What’s the best sextant? This
question leads to a compromise among four possible combinations of horizon
mirrors and telescopes. In writing my recent book, Celestial Navigation in the
GPS Age, I’ve studied these four combinations using nine different
sextants, giving me definitive but compromising views. Continue
reading…
Star finder tip
by Greg Rudzinski
There is more than one way to spin a
Rude star finder. Try the following technique the next time you shoot a round
of stars. Continue
reading…
How bright is bright
by Tim Queeney
At one time or another, virtually all
celestial navigators have looked at the data for the navigational planets and
puzzled at the cryptic numbers alongside the names. Some numbers are positive,
and some are negative, and they change over the course of the year. When he
asks about these labels, the navigator is told that the numbers represent
"magnitude," or the apparent brightness of the planets. And it helps
not at all to be further informed that the larger the negative number, the
brighter the object. Continue
reading…