Fortune Angles with Regard to Zodiacal Releasing
© 2010, Sept 21 Curtis Manwaring
I think that you are going to find variation between charts as to which to use based upon which factors are more "telling" (chrematistikos). The general idea is that in the first hours after birth one can use the 8th, the Moon, ascendant to see if the child is reared and makes it to an advanced age in childhood (3rd, 7th and 40th day of the Moon are said to have import here). This is where the natal 8th comes in more prominently. As we age, Schmidt has said that the fortune houses gain more potency. This is backed up in statements made by Valens that fortune houses are more "potent". The reason is that birth signifies potential (which is represented by the natal angles), but fortune because it is tied to the Moon (which effluents bring into manifestation) indicate an outcome on the concrete worldly level. So depending upon the chart, one might be able to use either. Sometimes planets for a given place will not readily testify, but other locations in the chart might do so.
When Valens speaks about the 8th from fortune, he is implying a method that should be pursued which is Zodiacal Releasing (aphesis) and that one should do this for the lot of fortune to see when the most dangerous times are bodily (in addition to other methods).