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Nautical Almanac altitude corr. changes
From: Bob Batten
Date: 2004 Apr 20, 11:23 -0400
From: Bob Batten
Date: 2004 Apr 20, 11:23 -0400
Fellow Navigators,
The message copied below has been received from a US Power Squadron
mailing list and should be of interest to all on this list.
---------------------- Forwarded Message: ---------------------
From: eddept-news-admin@usps.org
To: EdDept News
Subject: [EdDept-News] 2004 Nautical Almanac Altitude Correction Tables
Date: Mon, 19 Apr 2004 20:49:24 -0400
This list is intended to be a one-way broadcast of EdDept news to interested
United States Power Squadron recipients.
Please do NOT try to post any messages to this list.
Please ensure the following information is provided to all Junior Navigation
and Senior Navigation instructors, proctors, and students.
U. S. Naval Observatory has confirmed to the Offshore Navigation Committee of
the headquarters office of the United States Power Squadrons (Raleigh, North
Carolina) that the values for Altitude Corrections in the 2004 Nautical
Almanac have been slightly revised from earlier years. The changes are due to
a recalculation of refraction and affect the corrections for all bodies.
The Almanac pages affected are A2, A3, A4, xxxiv, and xxxv. Except for the
additional corrections for planets on page A2, these pages have been
considered permanent pages that do not change from year to year. With this
recalculation they are still considered permanent and are not expected to
change again in the foreseeable future.
The changes on page A2 for the Sun, Stars and Planets are limited to 0.1?and
because of the way the tables are arranged will be noticed in only a limited
number of cases. Page A2 for altitudes 0?-10? has changes of up to 0.7? at 0?
altitude but only spotty changes of 0.1? above 2? altitude.
Page A4 for non-standard conditions has been redrawn and another column added
to the table of corrections. This is where the majority of differences will
be found. The changes to the moon corrections on pages xxxiv and xxxv are
limited to altitudes below 4 degrees, and are 0.7? at 0? altitude. These
changes have an insignificant effect on practical navigation, but may cause
the values obtained to be slightly different than if the previous almanacs
were used.
The effects on the Junior Navigation and Senior Navigation courses are
described below. Please make sure this gets to all instructors and students.
The course material including homework and exams were developed prior to these
changes, and are based on the pre 2004 Altitude Corrections. The pre 2004
Altitude Correction pages, except for page A4, are included in the ?Excerpts
from the 199X Almanac? in both the Junior Navigation and Senior Navigation
course material.
For those not having access to a pre 2004 Almanac, a copy of page A4 is
available on the ONCom web page (see the "News" section). These pages should
be used to obtain values for Altitude Corrections for our courses.
Sight Folders should use the Altitude Corrections from the Nautical Almanac
for the year in which the sight was taken.
R/C Ken Barbour, SN
Chairman, Offshore Navigation Committee
ONCom@usps.org
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forwarded by Bob Batten
