Great question! I’m surprised no one has asked it before.
Although I can find no “authoritative Catholic explanation” of the Magi’s use of astrology, there is plenty of information to be found that explains this seeming contradiction.
First of all, it's important to understand that before the 17th century, astrology and astronomy were essentially the same pursuit. The stars were being used both observationally (for navigation) as well as for divination purposes (horoscopes).
This didn’t change until the advent of telescopic discoveries such as those by the Italian astronomer Galileo Galilei (1564-1642). When he and others found evidence of other celestial bodies that were not represented in astrological predictions, it began to cast doubt on the validity of astrology.
These doubts intensified with the advent of the printing press and the popularity of farmer’s almanacs that were based in astrology. When these published predictions failed, they did so in full view of the public.
Meanwhile, science continued to advance far beyond the realm of astrology and the two finally parted ways. Today, astronomy is based in the scientific understanding of the universe while astrology remains the stuff of tabloid prophecy.
The bottom line is that according to Matthew 2:2, the magi "saw his star at its rising" and followed it which means they were using it for navigation purposes in order to find their way to the Christ Child. This would indicate that the magi were not using the kind of astrology based in divination that the Church condemns, but were using it in a way that would later become known as astronomy.
Finally, it would not be plausible to assert that the Catholic Church would permit the use of any divination tool - be it astrology or conjuring spirits or reading omens - because attempts to divine the future are expressly condemned dating back to the earliest books in the bible, including Deuteronomy (18:9-14); Leviticus (19:26-31; 20: 6-27); and Isaiah (8:19; 47:13-14).
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