(TI-55 III) The Calculator and Its Use by the Mariner

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An excerpt from Merchant Marine Officers' Handbook, The Calculator and Its Use by the Mariner {chapter 5}, Fifth Edition (1989), pages 72-92

pg. 72 - picture of Texas Instruments TI-55 III calculator.
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                     CHAPTER 5
  The Calculator and Its Use by the Mariner
                    CAPTAIN KENNETH R. KIMBLE
THE calculator is an instrument which, when properly utilized, will assist the mariner by giving accurate, timely solutions to most of the day-to-day mathematical problems encountered aboard ship. …
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   Calculators come in many assorted shapes and sizes with various capabilities ranging from simple to complex.…
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   At present there are three basic keystroking systems: (1) algebraic, (2) algebraic operating (commonly used by Texas Instruments calculators), and (3) reverse Polish notation. The solutions to the problems within this chapter utilize the algebraic operating system on the keyboard of the TI- 55 III primarily because it more than meets the minimum requirements for the ideal calculator for the mariner and is the one with which the author is most familiar. …
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                                  SOLVING PROBLEMS
The use of the calculator can best be illustrated by completing problems that require the sine-cosine formula for their solution. In addition to having numerous keystrokes required it is the most flexible formula for use in celestial navigation. There are four major uses for this formula which can be accomplished through minor modifications to the entering arguments. They are
(1) the celestial solution of Hc and azimuth angle (Z);
(2) great circle distance, initial course angle, and final course angle;
(3) star identification-solving for meridian angle which when placed back into a star sight problem will produce sidereal hour angle, and the determination of declination;
(4) amplitude of a body whose center is on the visible horizon.
In order to provide continuity for the keystrokes involved, memory selection is of prime consideration. The following table provides the best placement of arguments for the problems indicated:
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                                     Solution of Hc and Z
The sine-cosine formulae for the solution of Hc and Z are as follows:
Procedure:
Keystrokes:
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           Finding Great-Circle Distance, Initial Course Angle,
                               and Final Course Angle
The second use of the sine-cosine formula, with some minor modifications, will give us great-circle distance (D), initial course angle (IC∠), and final course angle (FC∠).
Formula:
Keystrokes:
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          Use of the Sine-Cosine Formula for Star Identification
Formulae:
Remarks:
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                 Azimuth Angle (Z) for an Amplitude of a Body
                            Observed on the Visible Horizon
By using one of our sine-cosine equations we eliminate the necessity to enter tables 27 and 28 in Bowditch. Utilizing the information extracted we determine the azimuth angle and true azimuth (Zn) of the body and find the gyro error based on an amplitude.
Formula:
Keystrokes:
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                                   FUEL CONSUMPTION
Up to the time of the calculator, fuel consumption problems had to be solved in most cases by use of logarithms; however, they may be solved more quickly and accurately with the use of the calculator. Formulae for fuel consumption are as listed:
Keystrokes:
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BEST!
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