What is the relation between Astrology and Buddhism?

I come from a Japanese Zen background and currently practice in a Engaged Buddhist sangha under Thich Nhat Hanh. I have never heard of a connection with Zen Buddhism and astrology. That is not to say there is none though. And even if there is no historic connection between the two, if one is mindful they can see the dharma in all things. I do not have knowledge in astrology, but I would bet that if one looked at astrology with mindfulness that you could find the dharma there as well. May you be happy.

As far as I know, Buddhism doesn't have an overlap on Astrology.

In astrology, it is said that the planets and stars can affect on us and our future can be predicted according to that. So they also provide some remedies to survive from disasters as well. As for their explanation, astrology is an extended version of mathematics which uses the placements of planets to predict about people's behaviors.

But in Buddhism, it is said that everything that happens is based on what is being previously done/happened. So the people make their own fate from the things they do and the choices they make. It may be hardly depending on some planets and stars far far away. But it never says that astrology is false.

Personally, I have seen incidents where astrological predictions became true. And many cases where it haven't. But Buddhism, it is true. It's only a matter of fact how far you're gonna believe and understand it.

Hope this helped.

In DN 2 quoted below, the Buddha denounced practices like astrology, palmistry, divination, face reading, omen reading, magic, dream interpretation, predicting the future and so on as wrong livelihood and "animal arts" for monks. I highlighted the relevant parts.

"Whereas some contemplatives & brahmans, living off food given in faith, maintain themselves by wrong livelihood, by such "animal" arts as: reading marks on the limbs [e.g., palmistry]; reading omens and signs; interpreting celestial events [falling stars, comets]; interpreting dreams; reading features of the body [e.g., phrenology]; reading marks on cloth gnawed by mice; offering fire oblations, oblations from a ladle, oblations of husks, rice powder, rice grains, ghee, and oil; offering oblations from the mouth; offering blood-sacrifices; making predictions based on the fingertips; geomancy; making predictions for state officials; laying demons in a cemetery; placing spells on spirits; earth-skills [divining water and gems?]; snake-skills, poison-skills, scorpion-skills, rat-skills, bird-skills, crow-skills; predicting life spans; giving protective charms; casting horoscopes — he abstains from wrong livelihood, from "animal" arts such as these.

"Whereas some contemplatives & brahmans, living off food given in faith, maintain themselves by wrong livelihood, by such "animal" arts as: determining lucky and unlucky gems, staffs, garments, swords, arrows, bows, and other weapons; women, men, boys, girls, male slaves, female slaves; elephants, horses, buffaloes, bulls, cows, goats, rams, fowl, quails, lizards, rabbits, tortoises, and other animals — he abstains from wrong livelihood, from "animal" arts such as these.

"Whereas some contemplatives & brahmans, living off food given in faith, maintain themselves by wrong livelihood, by such "animal" arts as [forecasting]: the rulers will march forth; the rulers will not march forth; our rulers will attack, and their rulers will retreat; their rulers will attack, and our rulers will retreat; there will be triumph for our rulers and defeat for their rulers; there will be triumph for their rulers and defeat for our rulers; thus there will be triumph this one, defeat for that one — he abstains from wrong livelihood, from "animal" arts such as these.

"Whereas some contemplatives & brahmans, living off food given in faith, maintain themselves by wrong livelihood, by such "animal" arts as [forecasting]: there will be a lunar eclipse; there will be a solar eclipse; there will be an occultation of [a conjunction of the moon or a planet with] an asterism; the sun and moon will be favorable; the sun and moon will be unfavorable; the asterisms will be favorable; the asterisms will be unfavorable; there will be a meteor shower; there will be a flickering light on the horizon [an aurora?]; there will be an earthquake; there will be thunder coming from dry clouds; there will be a rising, a setting, a darkening, a brightening of the sun, moon, and asterisms; such will be the result of the lunar eclipse ... the rising, setting, darkening, brightening of the sun, moon, and asterisms — he abstains from wrong livelihood, from "animal" arts such as these.

"Whereas some contemplatives & brahmans, living off food given in faith, maintain themselves by wrong livelihood, by such "animal" arts as [forecasting]: there will be abundant rain; there will be a drought; there will be plenty; there will be famine; there will be rest and security; there will be danger; there will be disease; there will be freedom from disease; or they earn their living by accounting, counting, calculation, composing poetry, or teaching hedonistic arts and doctrines [lokāyata] — he abstains from wrong livelihood, from "animal" arts such as these.

"Whereas some contemplatives & brahmans, living off food given in faith, maintain themselves by wrong livelihood, by such "animal" arts as: calculating auspicious dates for marriages — both those in which the bride is brought home and those in which she is sent out; calculating auspicious dates for betrothals and divorces; for collecting debts or making investments and loans; reciting charms to make people attractive or unattractive; curing women who have undergone miscarriages or abortions; reciting spells to bind a man's tongue, to paralyze his jaws, to make him lose control over his hands, or to bring on deafness; getting oracular answers to questions addressed to a spirit in a mirror, in a young girl, or to a spirit medium; worshipping the sun, worshipping the Great Brahmā, bringing forth flames from the mouth, invoking the goddess of luck — he abstains from wrong livelihood, from "animal" arts such as these.

"Whereas some contemplatives & brahmans, living off food given in faith, maintain themselves by wrong livelihood, by such "animal" arts as: promising gifts to deities in return for favors; fulfilling such promises; demonology; reciting spells in earth houses [see earth skills, above]; inducing virility and impotence; preparing sites for construction; consecrating sites for construction; giving ceremonial mouthwashes and ceremonial baths; offering sacrificial fires; administering emetics, purges, purges from above, purges from below, head-purges; ear-oil, eye-drops, treatments through the nose, ointments, and counter-ointments; practicing eye-surgery [or: extractive surgery], general surgery, pediatrics; administering root-medicines and binding medicinal herbs — he abstains from wrong livelihood, from "animal" arts such as these. This, too, is part of his virtue."

In terms of horoscopes, it is definitely not a Buddhist practice to explain one's future or decisions based on some external forces (planets).

However, phases of the Moon have some importance in Buddhism. Many significant events in Buddha's life coincided with the Full Moon - birth, giving first teachings or death, to name a few. Full Moon is also considered to be the Amitabha Buddha Day (Buddha of Limitless Light and the principal Buddha in Pure Land Buddhism). One can find full lunar calendars where different Moon phases are associated with various Buddhas, practices etc. One example of observance days based on the lunar calendar is Uposatha when practitioners intensify their practice and make conscious effort to keep the 5 precepts.

One may wonder why bother with the Moon. In the simplest terms, the reasoning behind it is that our body is mostly composed of water and just like the oceans, the body (with its energy channels) does react to the Moon phases.

The main point is that the Moon phases are not used to predict one's future but rather to mark favourable or auspicious days for specific practises. One could coordinate one's practise with the Moon so that in different days one could focus on specific Buddha forms or teachings. So the Moon should be considered as a support and not an oracle of some sort. It might be helpful but it is not necessary to follow it.