I found these two items advertised on the Celestaire.com website:
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EMERGENCY NAVIGATION
by David Burch #5803 $16.95
A detailed account of how to find your position anywhere on the world's oceans after your electronics fail and you lose your sextant, watch, and almanac. The book is full of good sound navigational techniques and principles that will serve you well regardless of where and under what conditions you are sailing. You may never be confronted by a need for true emergency navigation, but even the most pleasurable sailing afternoon can be enlivened by a knowledge of the skills and methods taught in this book.

EMERGENCY NAVIGATION CARD
#4604 $12.95
A handy card to have on board in case your sight reduction system, sextant, or almanac becomes lost. The card is loose-leaf sized. You can punch holes in it if desired for insertion in a binder. It is plastic laminated for weatherproofing and durability. A wealth of information is provided on it in addition to: an emergency almanac for the sun, and declination tables for the stars; several methods for accomplishing sight reduction, including one that requires only the card itself; and angular markings on the perimeter of the card that allows approximate altitude measurements of celestial bodies.
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I don't plan to take up boating, let alone sail the Pacific single-handed using a sextant to navigate, but I am becoming increasingly fascinated by the human race's ability to navigate across thousands of miles of trackless ocean using mathematics (especially after reading Tami Oldham Ashcraft's "Red Sky in Mourning").

A Nautical Almanac and a set of Sight Reduction Tables is a bit heavy to take backpacking, but the above publications might well fit comfortably and not weigh too much. (Burch's book is listed at half a kilo; no weight is given for the Navigation Card, so I suspect it's probably negligible for anyone except the most fanatical ultra-lighters. <img src="/images/graemlins/laugh.gif" alt="" />

Has anyone used these or formed an (informed) opinion of them?