Astrology is concerned with natural cycles of the cosmological, rather than man’s version of made-up time. Astrological time is metered out in the eternal motion of the cosmos, and the natural cycles of the seasons here on Earth which are displayed in the twelve Sun Signs of the Zodiac. Therefore, an astrological Blue Moon is defined in astrology as a second consecutive new or full moon that falls in the same Sun Sign, which does not necessarily mean that they need to fall into the same calendar month. These back-to-back conjunct lunations increase the influence of the Sun Sign’s archetype, and projects both the first and last decan qualities that are magnified, intensified, and doubly emphasized during the stretch of time between them. These are the “Blue Moons” of astrology.
These Astrological Blue Moons are important in another way too, because they shift the soli-lunar (Sun/Moon) pattern of New and Full moons. The shift is significant from the astrological perspective in the sense that the Full Moon symbolizes the high lunar tide, or conclusion of the cycle and the completion of the astrological month, whilst the New Moon is the origin and starting point of a lunar cycle. A New to Full Moon pattern proceeds for around 18 months to which then a Blue Moon occurs, and the pattern shifts.