Astrology is about foretelling whether good or bad things will happen in the future on the basis of the positions of the sun, the planets and the stars. Astrologers cast 'horoscopes' which are supposed to tell you whether you will have a good week ahead or a bad one and whether you will be lucky in business or your love life. If you look in tabloid newspapers you will find horoscopes written for different 'star signs'. What star sign you are depends on what date your birthday is. It relates to the position of the sun compared to the constellations. If your sign is 'Pisces' it means that the sun was near the constellation Pisces when you were born.

Nowadays astrology is regarded as very unscientific and is made fun of by serious scientists. However, in the Middle Ages and Renaissance astrology just meant the practical bit of astronomy. It was taken very seriously by many people, including the most eminent scientific men of the time. Astrologers were often also leading astronomers and did many of their observations purely for astrological reasons. The mathematical instruments that astronomers used almost always had astrological tables and charts on them.