Only recently I came across a book written by the German mathematician and astrologer Nicolaus Rensberger. It has the slightly misleading title “Astronomia Teutsch”, or German Astronomy, and was printed in Augsburg in 1569.
We know that William Lilly published his Christian Astrology, an astrological textbook written in English, in 1647. 78 years before him Nicolaus Rensberger achieved something similar in Germany. He wrote the first astrological textbook in German. His book runs to about 800 pages and consists of four parts. Part 1 teaches the student the calculation of the positions of the Planets and the erecting of a birth chart. In part 2 he explains the meaning and effects of lunar and solar eclipses and revolutions. The third book teaches the interpretation of nativities and part 4 deals with directions and profections. Contrary to Lilly, Rensberger does not talk a lot about his sources. He mentions Ptolemy and makes some references to Arab astrologers, but does not go into too much detail. My intention in the future is to work my way through this rather voluminous book to find out which sources Rensberger used and how his material differs from that of contemporary British astrologers.
On of the differences I discovered in Rensberger’s book is his approach towards the Part of Fortune. He distinguishes between the day birth PoF: Moon-Sun+ASC, and the night birth PoF: Sun-Moon+ASC.
If we compare this to Lilly, who is basing his calculation on Ptolemy, we find that he only uses the day birth PoF for all nativities. He states in CA, p144: “Ptolomy, day and night takes it as above directed, with whom all practitioners at this day consent.” Lilly writes as well about the Part of Fortune: “Ptolomy does not more consider a Planet than the Part of Fortune, thus caracterized(glyph of PoF); it has no aspect, but any Planets may cast their aspect to it.” Further on he provides us with a table to calculate the strength of the Part of Fortune “in any figure”. We can see the positive or negative numerical values Lilly gives the PoF in sign, house and aspect to calculate the strength or weakness of it.
On the contrary we find in Rensberger: “Ptolemy does not value the Part of Fortune less than the Planets. But it has no aspects and the Planets do not cast any aspects to it, because it is only a point in the sky where the radii of Sun and Moon are.” He continues to produce the same table we can find in Lilly’s Christian Astrology, page 145, but as he states that the Planets do not form any aspects with the Part of Fortune, he substitutes it with the Sun. We find for example: The Sun is strong and fortunate in the signs of Taurus or Pisces 5, in Libra, Sagittarius, Leo or Cancer 4. The Sun is weak and unfortunate in the signs of Scorpio -5, Sagittarius -5 and Virgo -5 and in Aries she never gets or loses. He continues with the aspects in the same way and gives Sun conjunct Jupiter a value of 5, Sun conjunct Saturn -5 and so forth.
First I thought this to be an error, as I have already spotted some printing mistakes in his book. But in this case it seems to be how it was intended by Rensberger as he states in another place that “one has to look at the Part of Fortune by itself”.