Philosophically, the circle is the most perfect shape. According to Persian cosmology, rooted in both Natural science and Geometry and is a prerequisite of Astrology, there is no straight motion in the sky and any motion is defined as orbicular, circular or spherical.
Besides explaining astronomical planetary motions to find the mean or true planetary positions. Many astrological rules also developed based on these astronomical motions. The basic rule of spherical astronomy is very simple: If you understand the relation of two circles, you can understand the relation of every two circles. Therefore, by knowing 11 great circles in three coordinations, we can understand how different house systems, different methods of progression and unequal planetary aspects has been defined, calculated and used in astrological works.
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