## Sight Reduction Tables for Celestial Navigation
Sight Reduction is the process of solving the navigational triangle
for an assumed position and measured Altitude to obtain a Line-of-Position.
The Sight Reduction Tables available here are very similar to the tables issued
by the (former) "Defence Mapping Agency of the Hydrographic/Topographic Center"
as publication "H.O. 229".
Alternatively, the navigational triangle can be solved according to the
"Ageton Method". ## Purpose and Scope
The main purpose of these tables is to facilitate the practice of
celestial navigation at sea.
The tables have been designed for use with the "Marcq Saint Hilaire"
or "Altitude-Intercept" method of Sight Reduction, utilizing a position
assumed or chosen such that interpolation for Latitude and Local Hour Angle
is not required. ## ArrangementEach page of the table contains the Altitude (H) and Azimuth Angle (Z) values for the following ranges of arguments: - Latitude: one (integral) value
- Local-Hour_Angle: 10 successive (integral) values
- Declination: from 0° to 29° in integral values
(Declination*same as*OR*contrary to*Latitude: NN/SS or NS/SN )
Also the increment or decrement of the Altitude for the Declination
interval of 1° is tabulated (dH). This value can be used for
linear interpolation to obtain the correct Altitude value (Hc) for
the fractional (Degree/Minute) Declination value. ## Tables## Interactive Tables
## Pre-compiled TablesThe pre-compiled Sight Reduction Tables are available in PDF format. The complete Tables for 0° to 79° of Latitude (about 1000 pages) are divided over 16 Volumes, which can be selected from the table below. Each Volume has a Latitude range of 10°.
A worksheet for this table-based method of Sight Reduction is available as printer ready pdf file: worksheet for Sight Reduction using compiled Tables. ## Background Information
The Sight Reduction Tables as produced for the above scripts and files contain
tabulated values for the solutions of a spherical triangle of which two sides
(90°-Latitude and 90°-Declination) and the including angle
(Local Hour Angle) are known and the values of the third side (Altitude Hc)
and adjacent angle (Azimuth Angle Zc) are required.
The arguments for these formulas are Latitude (Lat), Declination (Dec)
and Local Hour Angle (LHA).
The values of the interactive tables are calculated with a JavaScript script using
the build-in "Math"-trigonometric functions.
I have compared at random about 100 sets of values from different argument combinations
with the corresponding values from the "H.O. 229" publications and found no significant
deviations other than "rounding errors". |

Cover << Sail Away << Celestial Navigation << . | last updated: 18-Sep-2018 |