Celtic Astrology Compatibility is a free test that finds your compatibility with your partner on the basis of Celtic astrology. Celtic zodiac is based on the Druid zodiac or Celtic Ogham Tree signs. An ancient mystical runic alphabet 'Ogham' led to the development of the Celtic astrology. Unlike the Western or the Egyptian astrology the Celtic astrology, also known as the Druid zodiac, comprises of 13 zodiac signs. The Druids were known to have been the inhabitants of the British Isles around 1000B.C. who followed a lunar calendar consisting of 13 months. The Celts visualized the universe in the form of a tree and for that reason they designated a particular tree, based on its magical properties, to each of the Moon phases in their lunar calendar. Each Celtic Zodiac corresponds to a particular tree and it is believed that an individual's personality is marked by the different influences of the tree of the sign.