This paper concerns computerization of the altitude correction in the sight reduction process. To obtain observed altitude, the factors such as refraction, parallx, semidiameter, phase etc, are corrected to sextant altitude. The factors are the arguments into the nautical almanac table from which are extracted values to add to or substract from the raw sight to obtain corrected value. If the altitude correction is to be done by sophisticated calculator, each factors must be formulated. The author studies the formulation of above factors, and simply from the date and ephemeris time of the sighting calculate the values of the factors. The calculated values are compared with that from nautical almanac, and it is confirmed that the formulae are practically used.