Yeah- I had heard something along those lines. That was a good part of what made me add MC: Starlock to the mix. I had even considered aiming for Master of the Starry Night, but too many of it's abilities are tied to Warlock's Curse mechanisms. (As it is, Celestial Scholar and Scion of Akhosia are frontrunning the paths.)
What's your character looking like so far? Have you considered picking up invoker? That would be very appropriate to the concept.
I don't really have any specific questions, just trying to spackle in some flavor/mechanic gaps.
Fair enough. I think I still suffer from some scholar-itis on the topic since it is such a vast area for me that when asked the simpering question "what's it about?" I am left stammering.
An important thing to keep in mind is that astrology (divination) and astrometry (proto-astronomy) were often merged at the time. Though the differentiation of the two has interesting story potential. And what we think of as astrology, well the Arabian philosophers really had some extraordinary ideas.
For example, medical astrology. With sufficient information about a subject's astrological chart a skilled practitioner was believes to be able to perform remote healing - a combination of faith healing and supernatural diagnosis (with a speedy messenger to communicate the astrologer's findings).
A common thread among astrological thinkers was the concept of fate, a divine plan governing mortals which was immutable. Thus there was an opportune moment for everything. Know and act on it and you would likely succeed; fail to take it into account and your endeavor was likely to fail.
An interesting conflict arose when a group of philosophers (which typically went hand in hand with alchemy, astrology, and poetry) questioned the supremacy of fate. Basically they argues that "destiny" existed and "fate" did not, which could be seen as a heretical idea. The astrological idea is that the stars could lead an individual to what they were put on this earth to accomplish, but that was entirely mutable by the individual's actions.
In the first case the stars are surely divine, but they can also be oppressive.
In the second case the stars are a mix of divine but since they're not perfect windows into the future they would also be arcane/magical entities. Interestingly they are not usually seen as oppressive. If you went with this idea (which fits better for a pious warlock), interpret the pact as something not laced with evil, but your PC could be at odds with the religious heterodoxy.
The most poetic description of astrology from Arabian philosophers I've heard is "destiny from eternity foreordained."