If your asking if the magical practice of being an Astrologian can originate anywhere else but Sharlayan then no.
If you're asking if you can have a Keeper that had a fascination with stars and constellations, Ewer in particular, well then....Yes. Perhaps that will lead them to seeking someone out to teach them Sharlayan Astromancy.
If you're asking if you can have a Keeper that had a fascination with stars and constellations, Ewer in particular, well then....Yes. Perhaps that will lead them to seeking someone out to teach them Sharlayan Astromancy.