Sterneck method

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The Sterneck method is a standard method of astrometry and geodetic astronomy for determining the pole height (astronomical or geographical latitude ).

The zenith distance  z of stars is measured when they cross the meridian ( upper culmination ), from which the latitude φ results from the known declination δ of the star :

  • For southern stars φ = δ + z
  • For north stars φ = δ - z .

The astronomical refraction and the possible influence of the telescope bending must also be attached to the measured zenith distance . When observing north stars at lower culmination , the supplement angle 180 ° −δ should be used instead of  δ .

If stars are selected in pairs so that their northern and southern zenith distances are approximately the same, the influence of a few small instrument errors and any systematic errors in refraction due to temperature or air pressure are eliminated . This is why the Sterneck method is one of the most precise methods for determining astronomical latitude, in which the horizontal passage of the stars also allows the trained eye to largely eliminate the influence of air turbulence on the horizontal thread of the thread network .

With a second theodolite , when measuring three to six pairs of stars, accuracies of ± 0.2 ″ to ± 0.5 ″ can be achieved, with a universal or passage instrument approximately ± 0.05 ″ to ± 0.1 ″. Together with a length determination from meridian passages or with the astrolabe , this is the classic method for determining exact deviations from the perpendicular . A variant without circular readings, the Horrebow-Talcott method, was developed for the measurement of the polar motion , which was previously carried out astronomically .

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