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| wiki:astronomy [2023/11/11 19:43] – Roy Prouty | wiki:astronomy [2023/11/14 12:25] (current) – Roy Prouty |
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| The word "astronomy" comes from the Greek //astronomos// meaning "of the management or arrangement of stars". This arrangement of stars onto maps or other records (written or verbal) allowed our ancestors to notice patterns that have served as the basis for modern time-keeping and navigation. Modern star maps make use of one or more systems of celestial coordinates. These coordinates are generally spherical coordinate systems centered on the observer([[~coordinate_systems|Horizontal/Alt-Az]]), the Earth([[~coordinate_systems|Equatorial]]), or the Sun([[~coordinate_systems|Ecliptic]]). | The word "astronomy" comes from the Greek //astronomos// meaning "of the management or arrangement of stars". This arrangement of stars onto maps or other records (written or verbal) allowed our ancestors to notice patterns that have served as the basis for modern time-keeping and navigation. Modern star maps make use of one or more systems of celestial coordinates. These coordinates are generally spherical coordinate systems centered on the observer([[~coordinate_systems|Horizontal/Alt-Az]]), the Earth([[~coordinate_systems|Equatorial]]), or the Sun([[~coordinate_systems|Ecliptic]]).\\ \\ |
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| | Another common procedure in this arrangement of stars is to arrange them by brightness. A relative brightness scale called the magnitude system has changed over the years, but we now use a fairly robust [[~:magnitude|magnitude system]] to organize stars by relative brightness.\\ \\ |
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| | For absolute units, we will use the SI system of units. These --- as well as their spectral counterparts --- constitute the absolute scale of physical quantities we can use to arrange stars and other sources. See [[~:radiative_quantities|radiative quantities]] for more information on these. ((See [[~:magnitude|Magnitude System]] for an idea of how to change between the two scale types.)) |
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