The Answer Box
Rachel: Why don’t astrologers use declinations? They seem important to me.
Zip: I suspect that the main reason they are not used more is that they require an additional computation. The commonly used aspects in astrology (and even most of the uncommon ones) are derived from the longitudinal positions of the planets. The circle can be divided by any whole number up to twelve (and some go even farther), or by fractions such as 3/8 or 5/12, to get aspects in longitude. Longitude is, of course, derived from the distance the planet is along the ecliptic from the spring intersection of the ecliptic and the equator—the point we call Zero Aries. The other dimension of the coordinate system is latitude or the distance the planet is above or below the ecliptic. Very few astrologers use latitude, though it can be important if two planets are very close to the same latitude, either north or south. But since most planets stay close to the ecliptic, the possible range is not very big, and they have to be within a few minutes of each other to be important.
Declination is part of a different coordinate system which measures north and south from the equator (declination) or around the equator from Zero Aries (right ascension). Right ascension is used in Primary Directions and in Parans, the latter another type of aspect which uses only the four major angles of the chart—Ascendant, MC, Descendant, and IC. In general, the astrologers who have tried right ascension have concluded that it did not work as effectively as longitude. On the other hand, most of the astrologers that I know who have tried declination do feel that it is a useful tool, providing a potentially valuable aspect—the parallel if two planets are within one degree of each other, both north or both south, or the contra-parallel if one is north and one south within one degree. The parallel does have to be exact within one degree, which means the exact minute has to be calculated. Most ephemerides give declinations only every third day, so some interpolation is required, and I suspect that most astrologers just do not bother to do the additional calculations.
My own experience is that the parallel is a useful aspect, much like a conjunction though not as strong, while the contraparallel is similar to an opposition. I do feel that if two planets have both an aspect by longitude and a parallel or contraparallel, the combination becomes very important—an indication that those two parts of the individual’s nature are deeply meshed and interacting. I have seen some interesting results with parallels helping to differentiate between twins, using parallels to the angles of course. I agree with you that they are important aspects and worth including in our kit of tools in astrology. Interpretation will of course depend on the nature of the planets involved, as well as on the house and sign and any other aspects to the planets forming the aspect. Two planets which normally relate easily to each other are usually easier to combine than two which symbolize parts of life where there is natural conflict such as Mars and Saturn—self-will meeting the limits of self-will. Any combination of the different parts of life can be positive if we know what we are doing, but some call for more awareness. So do continue to work with parallels, and maybe your question will encourage others to do the same.