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    Re: Sight reduction methods
    From: Gary LaPook
    Date: 2015 Nov 4, 10:37 -0800

    I wrote a series of posts comparing various methods of sight reduction, see:






    Also check out the Flat Bygrave, easily made at home. If you don't want to build one, and prefer using electronic calculators, then try out the Bygrave formulas on your calcualtor, easier to use than LOC and, if all you need is an azimuth, then that method produces the azimuth first, much shorter than LOC. If you want to use a standard slide rule then the Bygrave formulas are more accurate than the LOC done on a slide rule, that has been anaysed here in the past. 










    Re: Sight reduction methods
    From: Stan K
    Date: 2015 Nov 4, 09:49 -0500

    For those of you who like to play with various sight reduction methods, Celestial Tools (latest version is 5.0.1) includes "checkers" for the Law of Cosines (LoC) calculator method, the Nautical Almanac Concise method (NASR), Pub. 249 (formerly H.O. 249, Sight Reduction Tables for Air Navigation, A.P. 3270 in the United Kingdom), Pub. 229 (formerly H.O. 229, Sight Reduction Tables for Marine Navigation, H.D. 486 in the United Kingdom), H.O. 214 (Tables of Computed Altitude and Azimuth.  Can use delta d only; both delta d and delta t; and delta d, delta t, and delta L), H.O. 211 (Dead Reckoning Altitude and Azimuth Table, Third Edition, known as Ageton, and the Modified H.O. 211 Compact Sight Reduction Table, known as Ageton-Bayless), H.O. 208 (Navigation Tables for Mariners and Aviators, Sixth Edition, known as Dreisonstok), and two versions of the S-Table (Pepperday and Farley).
    I have also uploaded to this group checkers for the recently-discussed hav-Doniol and Ageton Classic methods.

    -----Original Message-----
    From: Robert VanderPol II <NoReply_RobertVanderPolII@fer3.com>
    To: slk1000 <slk1000---.com>
    Sent: Wed, Nov 4, 2015 5:42 am
    Subject: [NavList] Re: Sight reduction methods

    Sight reduction methods
    From: Dale Bletso
    Date: 2015 Nov 3, 12:30 -0800
    How many different methods are there for sight reductions.  I have used Law of Cosines, NASR, HO211 (Ageton) and HO229.  I also know of HO249 but have not used it. Just curious.
    In addition to various early methods using  Sine&Cosine Tables and Haversine Tables which I have limited knowledge of the following are some of the major manual systems widely used during the 1900’s (at least within certain niches) or that are currently seeing development.  The most commonly used names are underlined:
    Bygrave /Air Ministry Laboratories Position Line Slide Rule (1920), Tubular slide rule 3”dia X 9” Long,  Altitude to about 1’ and azimuth to 1o.
    Weems Line of Position Book/A short accurate method using Ogura's altitude tables and Rust's modified azimuth diagram (1928)

    H.O.-208/Navigation Tables For Mariners and Aviators/Dreisonstok (1928)


    H.O.-211/Dead Reckoning Altitude and Azimuth Tables/Ageton (1931) 36 pages, Estimated Position, Tables of Log-secant and Log-cosecant,  Results degrade when intermediate result K is near 90o or 270o. Altitude to 0.5’ and Azimuth to 1o.

    H.O.-214 /Tables of Computed Altitude and Azimuth/H.D.#486 (in UK) (1936 -46) 9 volumes, all celestial bodies.  Altitude to 0.1’ and azimuth to 0.1o.  Assumed position.

    HO-218/Astronomical Navigation Tables (1941).

    Brown-Nassau Spherical Computer(1942-5) circular slide rule,12” square X ¼” thick. Assumed position, Altitude to about 5’ and Azimuth to 1o. Solutions worked in about 1 minute of time.
    H.O.-229/Sight Reduction Tables for Marine Navigation  (1945ish )Assumed Position, 6 volumes, all celestial bodies, Altitude to 0.2’ and azimuth to 0.1o. (Replaced HO-214 for US Navy use in 1971), double second difference interpolation may be required required for altitudes above 60.and altitude accuracy can degrade to 0.3’ or so.
    H.O.-249/Sight Reduction Tables for Air Navigation/A.P. 3270 in the UK  (1947-53)Assumed position, 2 volumes plus a companion volume of pre-computed stars.  Only works for sun, moon, all planets and stars up to 30o declination.  Altitude to 1.0’ and azimuth to 1.0o.
    Doniol/Miniature Navigation Table for Altitude and Azimuth (1955) 2 pages, Altitude to 0.1’ and azimuth to 0.1o
    Reed's Nautical Almanac Method
    Compact Sight Reduction Tables/Bayless (1980), 9 pages,  Modified HO-211
    Sight Reduction Tables for Small Boat Navigation by Hewitt Schlereth (1983), Modified version of HO-229, Assumed Position to nearest even number, bodies to 29o declinations and AP to 59o latitude.

    Davies/Concise Tables for Sight Reduction/Nautical Almanac Office Sight Reduction;  (1984), 32 pages, Assumed Position, all celestial bodies, accuracy degrades when altitude nears 90o.

     S-Tables/Pepperday/ Celestial Navigation With the S Table, A Complete Sight Reduction Method for All Bodies in Nine Pages (1992), 9 pages, Modified HO-211
    LaPook / Flat Bygrave(2009) Variation of Bygrave, 2 flat sheets,   
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