Explain how we view stars magnitude in the night sky and how that is different from the way astrologist study stars.

We view the magnitude of objects in the sky by comparing one to another,
assigning a higher-number magnitude to the dimmer one, and a lower-number
magnitude to the brighter one. 

This is different from the practice of astrologists/astrologers, because as far as
I know, they don't care about the magnitude of stars at all, and even if they do,
they certainly don't "study" the stars.

A,b,c is the answer to the question