You must read this to get a broad view of Vedic Astrology. It teaches you the foundations on which this vedic science is built. You need to know the 33 deva and understand the expansion of Vasudeva clearly. You need to understand the 8 lights called Asta-Vasu
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Foundation of Jyotish PDF
You can download three volumes of the teachings pertaining to the Foundation of Vedic Astrology. These are in zip archive and you need Winzip or any such software to extarct them.
Foundation Audiobook Archive