If one reads the available literature a case is made for both a tropical or a sidereal division of the mansions. Let us look at the arguments for both cases and examine how they can be put into practice.
The Sidereal argument:
The lunar mansions are based on positions of certain fixed stars that were originally used for orientation. It is argued that although the Arabians clearly used the tropical zodiac the lunar houses are quite clearly sidereal, particularly if one takes Al Biruni’s description in determining the lunar mansions in the astronomical part of his “The Elements of Astrology”. It is also argued that the determining name of the mansions is given by a major fixed star or grouping of stars. This argument however is also used to support the use of a sidereal zodiac. The only factor that is mystifying is how does one arrive at a clean division of the zodiac into 28 even parts of 12 degrees and 51 minutes? If you look for example at the distances between the defining stars of the first three lunar mansions, you can already see that they are not even! The distance between the group of stars that form the horns and brow of Aries (Sheratan/Mesarthim/Hamal) and the three stars that form the tail of Aries is for example much further away than that between these stars and the Pleiedes in the Shoulder of Taurus. The siderealists say that Tycho Brahe calculated the equal divisions (this I must admit I haven’t followed up). Another argument is that Ibn ‘Arabi occasionally refers to the Sphere of the Fixed Stars as the Sphere of the Stations and thus implies that they are sidereal.
The tropical argument:
Just as the signs of the zodiac are determined by the movement of the Sun (please refer to previous postings) so the lunar mansions are determined by the movement of the Sun and the Moon. The lunar mansions may be named after certain prominent stars but so too are the the signs of the zodiac named after constellations on the ecliptic! The equal division into 28 parts gives 4 septads, with each septad exactly equal to ninety degrees. That means with a tropical division each septad begins at 0 degrees Aries, Cancer, Libra and Capricorn respectively. There is another argument that favours a tropical division and that is that each mansion is determined by one sound/letter of the Arabic alphabet. The sounds being part of the Divine Breath of creation. The letters according to Ibn ‘Arabi are not accorded to the mansions but the other way around. The mansions arise out of the letters/sounds!
I am more inclined towards the tropical argument but if someone can give a more convincing argument for a sidereal attribution I am willing to listen! In the next posts I will try to tackle the difficult task of coming towards a signification for each of the mansions that might have a more practical astrological application than the very sketchy and not very satisfying “delineations” that are currently copied from one book to the next.