Abstract
It is desirable to get nautical almanac data from a digital computer through approximate calculation, when we fix ship's position with the computer by astronomical navigation. Fourrier series interpolation seems to be most suitable for the purpose, because right ascention and declination of a celestial body are nearly periodical functions. The author programmed formulas and calculated them with HITAC 5020E. Calculation time: About 0.005sec for R.A. (or E_*) and dec. of every fixed star, when 7 coeff. are used for each one of the factors. About 0.02sec for R.A. (or E_*), dec. and S.D. of the sun, 25 coeff. for every factor. Max. error: ±1.0sec, ±0'.1; ±1.2sec, ±0.'12, and ±1".0 respectively, where the coefficients are determined from Japanese nautical almanac (1967) data. If ephemeris data are used, maximum error will be reduced to a tenth of the above value. Recommendation: To put calculation formulas and accurate coefficients into print on a nautical almanac.
