McClure Jones’ 1978 Cast Down the Stars is a standalone fantasy novel.
Glory is a skilled astrologer, the Second Starcaster of the Solstice Tower. There’s no doubt that she will eventually be First Starcaster.
Her career has been complicated by her parentage. Her parents were traitors whose mad scheme got them (and their followers) killed. While society in general does not hold this against Glory, her grandfather Sun in Winter does, and he sits on the ruling Council.
Her parents are long dead but their greed still imperils the land.