Do you need a “guru” to learn astrology?
It depends on how you define “guru.” the literal definition is “heavy” which means a source that is full of the thing you seek. In this sense, yes of course you need guru to learn astrology, but that is no different from the need for guru to learn anything and everything. In every endeavor to gain something we don’t have we must seek it from a source that has it.
A very strong connotation of the word guru is a specific person who is heavy with the knowledge, talent or whatever that you wish to acquire. Concomitant with this connotation is the process of humble and faithful inquiry from this person, while rendering service and payments as tokens of gratitude and respect. Do we need that sort of guru to learn astrology?
It would be nice, if you can find an individual worthy of such dedication and trust. But it is not mandatory. Astrology is a skill. You can learn it from any guru, it doesn’t need to be a specific person it can be any good source of knowledge.
In the end the guru disciple relationship depends more upon the disciple than the guru anyway. Even with a traditional “guru” it is we who must make the effort to comprehend and internalize his or her instruction. This is true for every subject, even the most spiritual and ancient. Astrology as we currently practice it is among the least spiritual and ancient of the Indian sciences and arts. I do not subscribe to the notion that one must have a specific person formally accepts as a guru to become expert in astrology. But we should approach all sources of knowledge with the respect we offer to guru.