As it is not easy to find a step-by-step calculation guide for directions I am presenting one here. This is for the stout-hearted as the calculations involve 7 steps. But if done systematically, it doesn’t take that long.
They are based on Erich Carl Kühr’s calculation example in his book, “Berechnung der Ereigniszeiten”. Erich Carl Kühr (1899-1951), is a fairly unknown German astrologer. One of his great merits, are his tables for both Right Ascension and Oblique Ascension. He was a proponent for the use of Primary Directions, and did his best to make their calculation and use as simple as possible. You will need two sets of logarithmic tables if you want to do these calculations. The first is a table of goniometric, trigonometric logarithms. The second is a table of Proportional Logarithms for 0 to 179 degrees. Both tables can be found in the Useful Links section to the right.