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The contents of the almanacs have changed over the years from publications of lunar distances and the use of astronomical days to publishing the data in Greenwich hour angles and the use of Universal Time. The publication methods have progressed from hand set type for a letter press, to intermediate methods involving offset printing where the camera copy has been prepared on a tabulator and a card-operated typewriter. During the last decade electronic printing methods have been used where the flow of information at electronic speeds is automatic from the basic data to the printed page. The near future, with hand-held calculators, digital sextants wired to specialized computers, and shipboard computers promises even greater changes. The almanac for the computer might contain algorithms for calculating such items as steller positions, refraction corrections and solutions of the navigational triangle and Chebyshev series for calculating the hour angles of the Sun, Moon and planets. A realistic evaluation of the capabilities that the new computers and calculators can provide for celestial navigation indicates that the navigator will require, in addition to the present almanacs, data specially prepared for his calculator, machine readable tapes or cards containing the almanac, or algorithms which he can include in his computer programs. |
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