Your Co-Star is not your kundli, the gist

Your Co-Star is not your kundli

Two very different products are sold under the word "astrology" on the same app store, and the popular Western ones and the Indian ones compute different things, for different people, with different questions in mind.

This is the short way in. The essay has the working, the sources and the sky.

Put the same birth date, hour and town into a Western astrology app and an Indian one, and the sun usually comes back in a different sign on each screen. Neither app is broken. They are counting the zodiac from different starting points, and that is the smallest of the differences between them.

Every astrology app starts the same way. It asks for your birth date, your birth time and your birth place. From those three facts it works out where the sun, the moon and the planets stood in the sky at that moment. That list of positions is called a birth chart.

After that the two kinds of app go different ways.

One kind arrived from the West in a short burst: The Pattern and Co-Star in 2017, Sanctuary in 2018, CHANI at the end of 2020. Co-Star's own store page says it uses "NASA data" and that human astrologers work with AI on the writing. What these apps hand back is sentences. A short reading each day, a notification, a screen that compares your chart with a friend's, and paid reports about the year ahead or about someone you like. The Pattern calls what it makes "a psychological blueprint of one's self". The words come from therapy and self-help. There is no calendar in any of it.

The other kind is Indian and older on the store: AstroSage Kundli since 2014, Astrotalk since 2017, Astroyogi since 2019, InstaAstro since 2021. These hand back a kundli, extra charts made by dividing each sign into smaller parts, the moon's star out of twenty-seven, a table of dated life periods, a score out of thirty-six for matching two charts, and reports running past fifty pages. They also carry a panchang, the daily calendar, which tells you what today is in your own city: the lunar day, the day's star, sunrise, sunset, the festivals coming. And most of them open onto a list of astrologers you can call or chat with, charged by the minute.

The app store files all of them under Lifestyle. At home, both get called the horoscope app. So people judge one product by the other product's job, and come away thinking the whole subject is either too thin or too heavy.

Words decoded

birth chart: a list of where the sun, moon and planets were in the sky at the moment and place someone was born
kundli (कुण्डली): the same birth chart as Indian astrology draws it, usually as a square or diamond diagram
jyotisha (ज्योतिष): the Indian tradition of astronomy and astrology; the word behind "Vedic astrology"
panchang (पञ्चाङ्ग): the daily almanac: what kind of day today is, worked out for one city, the same for everyone standing in it
nakshatra (नक्षत्र): birth star; the moon's circle is cut into twenty-seven slices instead of twelve
dasha (दशा): the classical way of cutting a life into named periods with dates attached
ayanamsha (अयनांश): the setting that decides where the zodiac starts; change it and your sun can move a sign
natal: to do with birth; a natal chart is a birth chart

Why anyone should careBefore you decide which app is right, it helps to know what each one was built to have ready for you. One was built to describe your character. One was built to tell you what today is and then sell you a phone call. Knowing which is in your hand saves you from judging a whole tradition by a product that was never aimed at your question.

Read it properly, 7 min Your Co-Star is not your kundli