Hi Ed,
For the 9th parts, we count the prof. Asc from 0 degrees, not from its actual degree, like the Moon.
With Boris Becker, he has natal Asc at 9.22 Sag which profected to Lib when he turned 22 in the table I uploaded in my post above. For the 9th part calculation, we consider the prof Asc to be 0 degrees of the sign it has arrived to.
I have attached 9th parts table from Ben Dykes’ Introductions to Traditional Astrology book.
With Lib being month 1, Venus is the 9th part lord of the prof Asc.
We continue by counting 1 sign per month. The monthly prof Asc’s 9th part for Month 2 is Sco, ruled by the Moon.
The monthly prof Asc’s 9th part for Month 3 is Sag, ruled by Mars.
The monthly prof Asc’s 9th part for Month 4 is Cap, ruled by Saturn. And so on.
Another example: when a prof. Asc comes to Ari, Mars would be the 9th part ruler of of Month 1, Saturn would rule Month 2 - Tau, Venus would rule Month 3 - Gem, the Moon would rule Month 4 - Can, Mars would rule Month 5 - Leo, etc.