Implementing Swiss Ephemeris in JavaScript for Vedic Astrology

A comprehensive guide to using Swiss Ephemeris for accurate planetary calculations

Key Points

  • Swiss Ephemeris is the gold standard for astronomical calculations
  • We use Chitral/Lahiri ayanamsa for Vedic calculations
  • Proper error handling is crucial for astronomical calculations
  • Performance optimization techniques for heavy calculations

Getting Started with Swiss Ephemeris

Swiss Ephemeris provides highly accurate planetary positions essential for Vedic astrology calculations. Let's look at how to set it up and use it effectively.

Basic Setup
1import { createSwissEph } from '@swisseph/core';
2

3// Initialize with Lahiri ayanamsa
4const swe = createSwissEph();
5swe.setAyanamsa('CHITRAPAKSHA'); // Same as Lahiri
6

7// Function to get planet position
8async function getPlanetPosition(
9  planet: number,
10  julianDay: number
11): Promise<PlanetPosition> {
12  try {
13    const result = await swe.calcUt(
14      julianDay,
15      planet,
16      SEFLG_SIDEREAL | SEFLG_SPEED
17    );
18    return {
19      longitude: result.longitude,
20      latitude: result.latitude,
21      speed: result.speedLong,
22    };
23  } catch (error) {
24    console.error(`Error calculating position: ${error}`);
25    throw error;
26  }
27}

Error Handling and Validation

When working with astronomical calculations, proper error handling is crucial. Here's how to implement robust error checking:

Error Handling
1interface BirthData {
2  date: Date;
3  latitude: number;
4  longitude: number;
5  timezone: string;
6}
7

8function validateBirthData(data: BirthData): void {
9  if (!data.date || isNaN(data.date.getTime())) {
10    throw new Error('Invalid birth date');
11  }
12  
13  if (data.latitude < -90 || data.latitude > 90) {
14    throw new Error('Invalid latitude');
15  }
16  
17  if (data.longitude < -180 || data.longitude > 180) {
18    throw new Error('Invalid longitude');
19  }
20  
21  // Validate timezone using a library like moment-timezone
22  if (!moment.tz.zone(data.timezone)) {
23    throw new Error('Invalid timezone');
24  }
25}