# NavList:

## A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

**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:

http://fer3.com/arc/m2.aspx/Comparison-tabular-sight-reduction-methods-LaPook-jun-2011-g16648

http://fer3.com/arc/m2.aspx/Comparison-tabular-sight-reduction-methods-LaPook-jun-2011-g16653

http://fer3.com/arc/m2.aspx/Ageton-method-HO-211-LaPook-sep-2014-g28717

http://fer3.com/arc/m2.aspx/Question-Position-Calculation-LaPook-jan-2014-g26214

http://fer3.com/arc/m2.aspx/Question-Position-Calculation-LaPook-jan-2014-g26217

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.

See:

http://fer3.com/arc/m2.aspx/Bygrave-formula-accuracy-10-inch-slide-rule-Hirose-jul-2009-g8985

http://fer3.com/arc/m2.aspx/Bygrave-formula-accuracy-10-inch-slide-rule-LaPook-jul-2009-g9019

http://fer3.com/arc/m2.aspx/Longhand-Sight-Reduction-LaPook-jun-2014-g28000

http://fer3.com/arc/m2.aspx/Accuracy-Bygrave-LaPook-jul-2009-g8975

http://fer3.com/arc/img/128130.tinas%20bygrave.pdf

gl

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

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 methodsFrom:Dale BletsoDate: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.

__Bygrave__/Air Ministry Laboratories Position Line Slide Rule (1920), Tubular slide rule 3”dia X 9” Long, Altitude to about 1’ and azimuth to 1

^{o}.

__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 90^{o} or 270^{o}. Altitude to 0.5’ and Azimuth to 1^{o}.

__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 0.1

^{o}. 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 1

^{o}. 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 0.1

^{o}. (Replaced HO-214 for US Navy use in 1971), double second difference interpolation may be required required for altitudes above 60

^{o }.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 30

^{o}declination. Altitude to 1.0’ and azimuth to 1.0

^{o}.

__Doniol__/Miniature Navigation Table for Altitude and Azimuth (1955) 2 pages, Altitude to 0.1’ and azimuth to 0.1

^{o}

__Reed's__Nautical Almanac Method

__Compact Sight Reduction Tables/Bayless__(1980), 9 pages, Modified HO-211

^{o}declinations and AP to 59

^{o}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 90^{o}.

__-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*

__Flat Bygrave__(2009) Variation of Bygrave, 2 flat sheets,