Celestaire Nautical Almanac 2012 Edition. The Nautical Almanac is the cornerstone for all sight reduction. The only exception to this is that some Computers, and computer software provide the same data either in whole or in part. Even when this is the case, the Nautical Almanac also contains other data Such as sunset, twilight, star diagrams, and unusual celestial phenomena that makes it a good book to have available.