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    Re: Abhav sightreduction?
    From: Gary LaPook
    Date: 2012 Aug 1, 15:19 -0700
    "The only draw back is that the DR position is not used as the assumed position. "

    Which is only a drawback for those wanting to compute Hc from their own location so as to be able evaluate their practice sextant shots, it is not a problem for real navigation.

    gl

    --- On Wed, 8/1/12, Greg Rudzinski <gregrudzinski---.com> wrote:

    From: Greg Rudzinski <gregrudzinski---.com>
    Subject: [NavList] Re: Abhav sightreduction?
    To: NavList@fer3.com
    Date: Wednesday, August 1, 2012, 9:30 AM

    Orjan,

    My personal criteria for selecting back-up sight reduction tables:

    1. Error free.
    2. No form.
    3. Accurate enough.

    The hands down winner is Weem's Line of Position. This short table can be abridged to as few as 20 pages.

    I found that a form was not needed since there are only two extractions from the first table (degrees minutes and a trig log number). The second table has only one trig log extraction that is always added to the trig log value from the first table. Re-enter the second table with the trig log sum to get a calculated altitude. Azimuth is done by Rust diagram (two pages) very simple. It is very hard to beat something like this for an addition to any almanac.

    The only draw back is that the DR position is not used as the assumed position.

    Greg Rudzinski
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