Choose a school and settings

Every calculation in Ascendant depends on two settings, the ayanamsa and the house system. Together they are called AstroParams. This guide shows how to choose them for your use case, set them in code or from the environment, and confirm which ones a result used.

Pick settings quicklyCopy Anchor Link

The library defaults are KrishnamurtiVP291 with Placidus, so if you set nothing, you are working in the KP school. A single judgment should never mix the two schools. If your product offers both, run each one with its own settings, as shown in Use both schools in one app.

What the two settings doCopy Anchor Link

The ayanamsa is the offset that aligns tropical longitudes with the fixed sidereal zodiac. It changes every longitude Ascendant reports, for the Lagna and for each graha.

The house system decides where the twelve house cusps of the D1 chart fall. It affects D1 only. Divisional charts always use whole-sign houses, counted from their mapped Lagna, whichever house system you choose.

AstroParams are not part of the birth moment. They are settings of the calculation, and every chart calculation records the ones it used.

Set them in codeCopy Anchor Link

Provide the settings with AstroParams.layer when you build your runtime:

import { AstroParams, Swisseph } from "astro-ascendant";
import { Layer, ManagedRuntime } from "effect";

const runtime = ManagedRuntime.make(
  Layer.mergeAll(
    AstroParams.layer({ ayanamsa: "Lahiri", houseSystem: "WholeSign" }),
    Swisseph.SwissephCachedLayer,
  ),
);

AstroParams.layer takes an Options value, so TypeScript rejects any ayanamsa or house-system name the library does not know. Use AstroParams.DefaultAstroParams for the defaults, which is what Runtime.MainLayer uses.

See what changesCopy Anchor Link

The same birth, calculated under both presets, shows how much the settings matter. The birth is 2000-01-01 12:00 UTC at 12.9716° N, 77.5946° E.

The ayanamsa moves the Lagna by a fraction of a degree. That is small here, but it is enough to change a star, a sub lord, or a sign at a boundary. The house system moves the cusps. Whole-sign houses always begin at a multiple of 30°, and Placidus cusps do not.

Choose an ayanamsaCopy Anchor Link

Ascendant supports 47 ayanamsas, taken from the Swiss Ephemeris catalog. These are the ones most products use:

All 47 ayanamsasCopy Anchor Link

Pass any of these names exactly as written. They are listed in Swiss Ephemeris catalog order, not by how often they are used.

The AstroParams reference shows the same list as a type.

Choose a house systemCopy Anchor Link

Ascendant supports 13 house systems. Placidus is the default.

Use both schools in one appCopy Anchor Link

Build one runtime per school and send each judgment to the right one. This keeps KP and Parashari results from mixing:

import { AstroParams, Swisseph } from "astro-ascendant";
import { Layer, ManagedRuntime } from "effect";

export const kp = ManagedRuntime.make(
  Layer.mergeAll(
    AstroParams.layer({ ayanamsa: "KrishnamurtiVP291", houseSystem: "Placidus" }),
    Swisseph.SwissephCachedLayer,
  ),
);

export const parashari = ManagedRuntime.make(
  Layer.mergeAll(
    AstroParams.layer({ ayanamsa: "Lahiri", houseSystem: "WholeSign" }),
    Swisseph.SwissephCachedLayer,
  ),
);

Then run a calculation with the runtime that matches the question, for example kp.runPromise(Chart.generate(located)). Dispose both at shutdown.

Read the settings from the environmentCopy Anchor Link

AstroParams.layerConfig reads the settings from Effect Config, so you can choose them per deployment without code changes:

import { AstroParams, Swisseph } from "astro-ascendant";
import { Config, Layer, ManagedRuntime } from "effect";

const settings = AstroParams.layerConfig({
  ayanamsa: Config.schema(AstroParams.Ayanamsa, "AYANAMSA"),
  houseSystem: Config.schema(AstroParams.HouseSystem, "HOUSE_SYSTEM"),
});

const runtime = ManagedRuntime.make(
  Layer.mergeAll(settings, Swisseph.SwissephCachedLayer),
);

Run it with the variables set:

AYANAMSA=Raman HOUSE_SYSTEM=Equal bun run app.ts

A name the library does not know, such as AYANAMSA=Nope, fails the program with a ConfigError whose message lists the accepted values. Your app stops at startup instead of producing a chart with the wrong settings.

Confirm which settings a result usedCopy Anchor Link

Each chart calculation carries the settings it was made with:

const calculation = yield* Chart.generate(located);

console.log(calculation.astroParams);
// { ayanamsa: "Lahiri", houseSystem: "WholeSign" }

Store or display this next to every result. A reading is only repeatable if you can say which ayanamsa and house system produced it.