angular distance travelled by the sun per day, which corresponds to around 360/365.25 degrees, in other words almost one degree. The use of different angular units can be surprising, but it is similar to the current situation in modern astronomy, where the angular unit used to measure angular distances between two points is certainly the same as for declination (the degree), but is different for right ascension (which is expressed in angular hours; an angular hour corresponds to exactly 15 degrees). In Chinese astronomy, right ascension and declination have the same unit, which is not the one used for other angular distances. The reason for this choice to use different units in the Chinese world is not well known. Meaning of units However, the exact value of these new units (zhang, chi and cun) was never stipulated, but can be deduced by the context in which they are used. For example, the spectacular passing of Halley's comet in 837 indicates that the tail of the comet measured 8 zhang. Even if it is not possible to know the angular size of the comet at the time it passed, it is certain that 8 zhang correspond to 180 degrees at the most (maximum visible angle on the celestial sphere), which means that one zhang can hardly exceed 20 degrees, and therefore one cun cannot exceed 0.2 degrees. A more rigorous estimation was made from 1972 on the basis of references of minimal separations expressed in chi or cun between two stars in the case of various conjunctions. The results suggest that one cun is between 0.1 and 0.2 degrees and that one chi is between 0.44 and 2.8 degrees, a range which is compatible with the estimations for one cun. A more solid estimation error is that it is generally accepted that one chi is in the order of one degree (or one du), and that one cun is in the order of one tenth of a degree. The expression "perhaps a few inches" therefore suggests an angular distance in the order of one degree or less. Problems with description If all the available elements strongly suggest that the star of 1054 was a supernova, and that in the area next to where the star was seen, there is a remnant of a supernova which has all of the characteristics expected of an object that is around 1000 years old, a