Amazon.com description: Product Description: A wealth of information is provided: an emergency almanac for the sun, and declination tables for the stars; several methods of 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. With this card and a watch you can find your way to any major port in the world. Other information includes how to steer by the stars and finding your boat's speed. A handy card to have in case your GPS, sextant, or almanac becomes lost. The card is loose-leaf sized. You can punch holes in it for insertion in a binder. It is plastic laminated for weatherproofing and durability.