Aldebaran is the bright white star in this image, representing one of the eyes of the bull in the constellation of Taurus.
Aldebaran was the most important star in the heavens to ancient astrologers because of its location in the very middle (15 degrees, 0 minutes, 0 seconds of arc) of the constellation of Taurus.
Aldebaran is traditionally seen as the lower eye of the "bull" and as a consequence was identified by the Arabs, Greeks and Romans as the "Bulls Eye," a phrase which has survived to the present day to describe the center of a target.
It was from this central position of Aldebaran that all other celestial longitudes were calculated, so much so that the Romans referred to it as "Stella Dominatrix," the "Master Star."
Aldebaran was, therefore, one of the four "royal stars" of ancient Persia along with Regulus, Antares and Fomalhaut.
Ancient astrologers also used the star Antares for locating longitudes, as it was located almost exactly 180 degrees from Aldebaran on the opposite side of the zodiac in the "heart of the Scorpion," at 15 degrees and 0 minutes of Scorpio. These were the two great "fiducial" stars of antiquity.
Note: In reality, there is really no such thing as a "fixed star," as these bodies of light are moving at incredible speed. It is only when viewed from our perspective on earth that they appear to be standing still. For example,
it will take the star Aldebaran approximately 90,000 years for it to move one degree in its proper motion as viewed from the earth.