What false assumption? And I am not an astrologer, nor am, dwelling upon the surface of this planet, any more in space than you or most other people are. Yet, I suppose, sometimes in order to challenge others' beliefs, you must start from an assumption of accepting them. Reductio ad absurdum, as it were... 

 One further consideration  among systems of divination, astrology alone seems to have problems with space travel. Consider e.g. numerology, or cartomancy (e.g. Tarot cards). Whatever different problems these systems may have, their applicability across different locations in the universe is not obviously an issue, unlike astrology.