Based on the Ancient Egyptian calendar which was based on lunar cycles of around 30 days and on the rising of the star Sothis (Sirius).
The celestial arch is represented by a disc held up by four pillars of the sky in the form of women, between which are inserted falcon-headed spirits. On the first ring, 36 spirits symbolize the 360 days of the Egyptian year.
On an inner circle, the constellations, showing the signs of the zodiac. Some of these are represented in the same Greco-Roman iconographic forms as their familiar counterparts (e.g. the Aries, Taurus, Scorpio, and Capricorn. Aquarius is represented as the flood god Hapy, holding two vases which have water pouring out - It is exactly the same as the Mesopotamian zodiac.
Below is the original carved map now shown @ the Louvre after being taken by Napoleons Troops