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2.1 The vertical cercle

The vertical cercle

This device enables the angular position of the Sun in the sky to be measured.

Do as Tycho-Brahé or Kepler did in the 16th century and note down its angular position: horizontally in comparison to the south and vertically above the horizon. 

Note down the azimuth and the height of the star and then compare them.

Return later and take a new reading. Vou will notice the variation in the position of the Sun, which results from the rotation of the Earth.