Data in this book are no longer valid for navigation. It is preserved in print because many training programs (including USCG and US Navy ) use examples from 1981 to teach celestial navigation. USCG license exams require data from this almanac. These exams also require Sight Reduction Tables, Pub 229, Vol. 2 and a 2102-D Star Finder. | The Nautical Almanac for the Year 1981 by Usno Nautical Almanac Office, Paperback | Indigo Chapters