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The process of predicting the heights and bearings of celestial sights before the sight session, and then choosing the best objects to use. This is the standard way to do star sights and also recommended for sights of Venus and Jupiter, even though they are bright and easy to find. With precomputed sights, you set the sextant to the predicted height, look in the predicted direction, and the star will appear in view near the horizon. To complete the sight, bring it in line with the horizon and record watch time and sextant height. Star precomputation can be done with Pub. No. 249, Volume 1, or with the 2102-D Star Finder which has the advantage of showing the best star-planet combination to use. Precomputation can also be done by standard sight reduction when you already know what sights you want. This is best done with a calculator, however, if you have many sights to precompute. See Pub. No. 249, Vol.1, Star Finder, Calculators, and Sextant Sights.

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