Hello Deborah,
I have been taking up this issue and have posted in astro.com. As I have also posted several charts, it might be easy, if you are interested, to go and check there:
http://forum.astro.com/cgi/forum.cgi?num=1320240310/20
Anyhow, for your easy reference, here's the Method which I myself find very good indeed, and is the same as you mention :
Truthin of Hermes:
1. AC/DC of the NEWBORN = Moon at conception
2. AC/DC of the MOTHER = Moon at conception
3. Radix Moon of the NEWBORN = AC/DC of conception chart
The Trutina Hermetis method of rectification is based on the assumption that the positions of the Ascendant and the Moon in the conception chart and the birth chart are interconnected by a rule: the Moon at birth is on the horizon axis of the conception horoscope, and the Moon at conception is located on the horizontal axis of the radix.
In classical form the Trutina Hermetis says:
? When the radix Moon is waxing Moon and above the horizon, the period of pregnancy was less than 273 days, and the Moon in the prenatal epoch chart is conjunct the Ascendant of the radix.
? When the radix Moon is waning Moon and above horizon, the pregnancy was more than 273 days, and the prenatal Moon has the same coordinate as the Descendant of the radix.
? When the radix Moon is under the horizon and waxing, pregnancy was more than 273 days, and prenatal Moon incorporates the radix Ascendant.
? When the radix Moon is under the horizon and waning, pregnancy last less than 273 days, and the prenatal Moon conjoins the Descendant of the radix."
On the birth chart of the child, see where the moon is. According to its position, example:
AC 20? Scorpio
Moon 20? Cap
Difference: 60?
If waxing moon at birth, you divide 60:12 = 5
The baby was 5 days later that alfa day 273
The usual range is from 258 - 273 - 288
Check the various options above and off you go
