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    Nautical Almanac altitude corr. changes
    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
    EdDept-News mailing list
    forwarded by Bob Batten

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