Sight Reduction Tables H.O. 249, Vol. 3: Latitudes 39-89
by National Imagery and Mapping Agency
Volume 3 of a 3-volume set covering latitudes 39-89. Precomputed tables of altitude and azimuth designed for the rapid reduction of astonomical sights in the air. Commonly used by marine navigators where their greater convenience offsets the less precise positional data derived. Good forever.