NavList:

It's highly unlikely that Hewlett-Packard engineers were thinking about celestial navigation when they introduced the first scientific pocket calculator, the HP-35, in 1972.  Desktop scientific calculators, able to carry out computations required for navigation, had existed since the late 1960s.  Since they were heavy, large devices which required AC power, they would have been suitable for the bridge of a navy or merchant marine ship, or the navigation station of a grand yacht, but not for the chart table of a smaller sailboat. Portable, battery-powered calculators became available in 1971. These were only able to carry out the four basic arithmetical operations, so they could not be used for calculations that were traditionally carried out with tables of trigonometric and logarithmic functions, or slide rules. The HP-35, which had transcendental functions, could do all this running on batteries, and fit in a shirt pocket.  It was soon followed by similar calculators from Texas Instruments and other companies.  Two years later, Hewlett Packard introduced the first programmable pocket calculator, the HP-65. A program consisted of sequence of keystrokes stored on a magnetic card, which allowed repeating calculations with even more ease.  As with its predecessor, other models by this and other manufacturers came along in a few years.

These early calculators did have some disadvantages when compared with slide rules or tables: if their batteries died, or if they were submerged in seawater, they were likely to become only marginally useful only as chart paperweights (Frank Reed has pointed out that some current models have overcome these problems by being solar powered, and being unaffected by seawater).  But the ease with which they allowed solving the navigational triangle, among many other uses, did no go unnoticed, and books describing the use of scientific pocket calculators in navigation followed. As an example, the second version of Capt. H.H. Shufeldt’s “Slide rule for the mariner”  (1972) became “The calculator afloat: mariner's guide to the electronic calculator” (1980).  One attractive advantage of the use of calculators to reduce a sight is the clarity with which one can see that one is solving for one of the variables of a navigational triangle.  Although this is also the case when using sight reduction tables, this fact may be less immediately obvious at first sight.   This may be even more relevant for those who, like me, are celestial navigation enthusiasts, rather than actual or “real”navigators. After all, for a “real” navigator, the crucial objective is determining an accurate position, or making a successful landfall, regardless of the underlying theory. Instead, for the enthusiast, the process is as important as the result, and the “why” matters as much as the “how”.  And the scientific pocket calculator, now half a century old,  is an ideal tool for the study of this fascinating hobby.

Best wishes,
RafaelC

P.S.  Perhaps I should add that I’ve never had any financial interest in the Hewlett-Packard corporation.  In any case, scientific pocket calculators are used mainly by high school students at this time, and I’ve read that H-P has shut down its calculator division, and just adds a logo to a few calculator models designed and made in China. But I cannot deny that I'm an H-P calculator fan.  I can’t be the only one left, as improved clones and free software simulators of some of their classic models are still being developed.