AUTHOR’S NOTE: The Golden Dawn’s alignment of the tarot cards with the astrological (aka “Chaldean”) decanates (36 ten-degree segments of the zodiac beginning on the Vernal Equinox) has intrigued me since I first picked up the tarot in 1972 to complement my practice of astrology, but I have never been satisfied with its customary application to timing and I find limited use for its “card-of-the-day” specificity. Consequently, I’ve been on something of a crusade to find more inspiring uses for the concept of “decans,” and I’ve written a number of previous essays on the subject (a few of which are linked below). Here is a summation of my efforts.
One notable thing about assigning the tarot cards to the zodiacal decans (or at least 68 of them, leaving out the seven planetary and three primary-element trumps) is that every card has a counterpart directly opposite it on the wheel. I’ve used this fact in creative experiments that I once characterized as embodying a “tension-and-release” paradigm that brings to mind shooting an arrow from a bow.
When a card comes up in a reading that doesn’t seem to make sense within the context of the question or topic, it can be instructive to consider its polar opposite as conveying “the rest of the story” regarding its significance to the sitter’s circumstances. This is particularly useful with the Minor Arcana, not so much with the court and trump cards. This assumption acknowledges that no card functions in a vacuum; they are all part of an intricate matrix with diametric “regard” being a special type of correlation. Reading pairs in this way can round out the perspective with remarkable clarity, and I treat the linked partners as furnishing a population of “built-in clarifiers” whenever one or the other is pulled.
Another approach I’ve used involves reversed cards that present a similar but more complicated conundrum. I will examine the “opposite number” (always in its upright orientation) to see if it offers a “way out of the box.” It’s notable that any pair of opposing pip or court cards is always of the same elemental polarity (Fire and Air are “positive,” Water and Earth are “negative”), at least placing them in the same operating arena of active or passive reaction to the dilemma. (I once called them “Chaldean mirrors.”)
A good example for both of the above scenarios is presented by the 10 of Swords (third decan of Gemini) and the 10 of Wands (third decan of Sagittarius); in the latter, the challenge, while still considerable, is more-or-less “in hand” and not hung on the victims back like the “Kick Me” sign of the practical joker, making for a more manageable situation. Rather than having to content ourselves with gazing wistfully at the rising Sun in the Waite-Smith 10 of Swords, we are offered an “in-process” solution with which we can engage directly.
Becoming even a bit more fanciful, at one time I proposed enlisting the polar duets in a different method of deriving the “shadow card,” a step that is normally done by revealing the bottom card of a shuffled deck. Once again, the target card resides within the architecture of the Chaldean array rather than being completely arbitrary, betraying my desire for a measure of logical structure when applying auxiliary cards as clarifiers (although that’s a topic unto itself that has inspired a number of curmudgeonly rants).
Realistically, these innovations and their ilk are philosophical rather than literal, but they create a flexibility of interpretation that cooperates well with other more impressionistic modes of tarot divination.
Parsifal's Wheel Tarot & Astrology 