Bessel Besel Fr.: Bessel From Friedrich Wilhelm Bessel (1784-1846), German astronomer and mathematicians, who made fundamental contributions to positional and spherical astronomy. |
Bessel equation hamugeš-e Besel Fr.: équation de Bessel A linear second-order differential equation, the solutions to which are called Bessel functions. Hamugeš, → equation. |
Bessel's star setâre-ye Bessel Fr.: étoile de Bessel Same as → 61 Cygni, the first star whose distance was measured, by Friedrich Bessel in 1838. |
Besselian Besseli Fr.: besselien, de Bessel Of or pertaining to Friedrich Wilhelm Bessel (1784-1846) or to his discoveries. → Besselian day number → → Bessel equation → Besselian star constant → → Besselian year. → Bessel. |
Besselian day number šomâre-ye ruz-e Besseli Fr.: Any of the five quantities denoted by A, B, C, D, and E used in conjunction with → Besselian star constants for the reduction of a star's → mean catalog place to its → apparent place. |
Besselian star constant pâyâ-ye axtari-ye Besseli Fr.: constante stellaire besselienne Any of the eight quantities denoted by a, b, c, d (for → right ascension) and a', b', c', d' (for → declination) used in conjunction with → Besselian day numbers for the reduction of star's → mean catalog place. |
Besselian year sâl-e Beseli Fr.: année besselienne The period taken for the right ascension of the mean Sun to increase by 24 hours. The starting point is when the mean Sun's longitude is 280°, corresponding roughly to January 1. It is virtually the same as the tropical year. |