Does a magic focus in an astrological house, sign or planet effect Hermetic Divination (Astrology)? If so how?
The text of magical focus says "When you cast a spell or generate a lab total" so by a strict reading; no it does not.
Depending upon how powerful the focus is I'd probably allow it. Some of the astrological house focuses are exceptionally narrow and hermetic divination could certainly use some help.
Not for the ruled, but it is so thematic i would allow it for sure if your query is made during the period the sign is in the sky or if it relates to the sign. Sounds cool, mystical and as it should be IMO. ArM5 has lost some of that mysticism along the rules creep and i think it gets better when you bring that aspect of magic back.
Cheers,
Xavi