It has also been re-written depending on the religion, Catholics, Mormons, Lutherans, Christians etc all have different versions of the bible, although they are all basically the same, for example Mormons have the King James version.
As for the astrology part, constellations and astrology have always been a main stay of religion, the north star is what led the prophets to baby jesus after all.
Astrology was very very important to our ancestors, you can tell the time of year depending on the location of the stars and constellations. Orion is also one of the brightest ones in the southern hemisphere so it would be easy to see.