Right ascension

The sun's right ascension in time is useful to the practical astronomer in regular observatories, who adjusts his clock by sidereal time.

The right ascensions and declinations obtained by the preceding calculations, are the mean values, to which must be applied the corrections for the Nutation and Aberration Tables XLII. XLIII. in cases where great accuracy is required, as is now done in the Nautical Almanac for 24 of the brightest stars for 10 days in the year, and those numbers in the Nautical Almanac are to be preferred.

1988, Peter Duffett-Smith, Practical Astronomy with Your Calculator, page 35, The hour-angle, H, and the right ascension, α, are related by the simple formula H = LST − α, where LST is the local sidereal time.