Celestial Navigation with the S Table

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Review Author: Henry Cordova
Celestial Navigation with the S Table
by Mike Pepperday (1992)

Like most navigators, I originally learned how to perform sight reductions with the venerable Sight Reduction Tables for Marine Navigation (HO 229). For those not familiar with this work, it is a set of six hard-cover volumes, each 10" x 12" and weighing about 3 1/2 pounds each. Many small boat sailors prefer the more compact Sight Reduction Tables for Air Navigation (HO 249) in three volumes, each the same size and weight as HO 229, although the reduced format was paid for by certain restrictions on use and generality. The complete HO 249 can be purchased for approximately $120, while its larger cousin costs over twice as much. Although both of these items are available in smaller paperbound commercial editions at a substantial discount, we are still talking a substantial investment and a lot of valuable space, particularly for the mariner who only sees celestial as a backup to his electronics.

Today, most celestial navigators use pocket calculators to reduce their sights, either dedicated models specialized for this purpose or programmable devices with user-written or commercially published software. Some sailors have been known to use laptops or even desktop PCs with full-blown "Navigation Packages" installed. I always thought this was like putting an air conditioner in a stagecoach, but... to each his own.

The primary justification of celestial navigation, other than the pride taken in even having the ability and skill to do it, is as an independent backup to GPS, and as much as possible to be able to overcome the vulnerabilities of that system. These include power or battery failure, mechanical malfunction, hostile jamming or friendly spoofing of the signal in wartime; or even potential hazards such as solar flares, nearby supernovae, or electromagnetic pulse due to nuclear explosions or lightning strike. If the situation ever gets to the point whe

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