Getting Started with EclipseDB
31 Mar 2026 · RiSa Astronomy
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A Guide to Navigating 30 Millennia of Shadows
Welcome to EclipseDB, the world's most comprehensive digital catalog of solar and lunar eclipses, spanning from 13,000 BCE to 17,000 CE. Whether you are a researcher trying to date a 5th-century inscription or a curious observer looking for the next "Ring of Fire," this guide will help you master the tool.
1. Choosing Your Lens: Explorer vs. Archeo Mode
The site operates in two primary modes depending on your goal:
- Explorer Mode (Default): Best for general astronomy. It uses modern terminology (Saros series, Magnitude, TD — Terrestrial Dynamical Time) and is the quickest way to find future eclipses.
- Archeo-Astronomy Mode: Built for historians. This mode switches the calendar to Historical Years (where 1 BCE is followed by 1 AD) and adds Vedic parameters like Nakshatras, Rasis (Zodiac signs), and Indian Seasons (Ritus).
2. The Power of Filters
With over 142,500 eclipses in the database, the sidebar is your best friend.
- The Year Slider: Drag the handles to narrow down a century or a specific decade.
- Eclipse Type: Filter by Total (the sky goes dark), Annular (the "Ring of Fire"), or Partial.
- Advanced Logic: Expand the “Advanced range filters” section to filter by specific geographic coordinates or TropLon (the Sun’s tropical longitude relative to the seasons).
3. Understanding "Confidence Tiers"
Because Earth's rotation changes slightly over thousands of years (a value called ΔT), the exact "path" of an eclipse in 3000 BCE is harder to predict than one in 2026.
- Green / Certain: Precision within 60 km.
- Yellow / Regional: Good for general area identification.
- Purple / Speculative: The date is certain, but the shadow could have fallen anywhere in that hemisphere.
4. Interactive Maps & Planet Data
Click "More" on any eclipse row to open a deep-dive page.
- Solar Map: Features an interactive path. You can even adjust the ΔT slider to see how the path shifts if historical timekeeping varies.
- Planet Positions: See exactly where Mars, Jupiter, and Saturn were located during the eclipse — vital for verifying "multi-witness" historical accounts.
- Observer Tool: Pick a city (like Varanasi or Babylon) and click Compute to see exactly what the eclipse looked like from that specific ground location.
Tropical vs. Sidereal: Two Ways to Map the Sky
31 Mar 2026 · RiSa Astronomy
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The Tropical System (Seasonal)
Definition: This system is anchored to the Earth’s seasons. It begins at 0° Aries at the exact moment of the Vernal Equinox (Spring).
Precession: Because Earth wobbles on its axis (precession), the stars behind the equinox point change over time. In the Tropical system, the “Zodiac” moves with the Earth.
Use in EclipseDB: Used for the Ritu (Indian Seasons) and TropLon columns. It is the most reliable way to know if an ancient eclipse occurred during Spring or Winter, regardless of which stars were in the background 5,000 years ago.
The Sidereal System (Star-Based)
Definition: This system is anchored to the “fixed” stars. It does not move with the Earth’s wobble.
The Ayanamsha: The difference (offset) between the Tropical 0° and the Sidereal 0° is called the Ayanamsha. It grows by roughly 50.3 arcseconds per year as the equinox point precesses against the stars.
Use in EclipseDB: Used for Rasi and Nakshatra columns in Archeo-Astronomy Mode. The database stores all sidereal longitudes natively in the Lahiri ayanamsha; other systems are derived by applying a fixed offset.
Ayanamsha Models & the Rasi–Nakshatra Table
31 Mar 2026 · RiSa Astronomy
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1. The Ayanamsha Models in EclipseDB
Different historical and modern traditions use slightly different starting points for the Sidereal zodiac. EclipseDB lets you switch between four models. The database stores Lahiri natively; other systems are derived by applying a constant offset to the stored sidereal longitude.
| Model | Description | J2000 Value (approx) | Offset from Lahiri |
|---|
| Lahiri | Indian Government standard (Chitra Paksha). Default in EclipseDB. | 23.86° | — |
| Raman | B.V. Raman system; epoch where the zodiacs coincided circa 397 CE. | 22.47° | +1.39° |
| KP | Krishnamurti Paddhati; very close to Lahiri, used in stellar astrology. | 23.84° | +0.02° |
| Fagan-Bradley | Western Sidereal standard; anchored to the star Spica at 29° Virginis. | 24.75° | −0.89° |
Note on filtering: The Rasi and Nakshatra filters always operate on Lahiri boundaries (the stored database column). Switching the ayanamsha changes the displayed Rasi/Nakshatra labels in the table and detail pages, but the filter SQL query uses Lahiri natively. This is documented in the filter tooltip.
2. The Rasi & Nakshatra Table
In Archeo-Astronomy Mode, the 360° sky is divided into 12 Rasis (30° each) and 27 Nakshatras (13.33° each). Each Rasi contains exactly 2¼ Nakshatras. While the absolute boundaries shift depending on your chosen Ayanamsha, the internal structure remains constant:
| Rasi (Sanskrit) | Constellation | Nakshatras Included |
|---|
| Mesha | Aries | Ashwini, Bharani, Krittika (¼) |
| Vrishabha | Taurus | Krittika (¾), Rohini, Mrigashira (½) |
| Mithuna | Gemini | Mrigashira (½), Ardra, Punarvasu (¾) |
| Karka | Cancer | Punarvasu (¼), Pushya, Ashlesha |
| Simha | Leo | Magha, Purva Phalguni, Uttara Phalguni (¼) |
| Kanya | Virgo | Uttara Phalguni (¾), Hasta, Chitra (½) |
| Tula | Libra | Chitra (½), Swati, Vishakha (¾) |
| Vrishchika | Scorpio | Vishakha (¼), Anuradha, Jyeshtha |
| Dhanu | Sagittarius | Mula, Purva Ashadha, Uttara Ashadha (¼) |
| Makara | Capricorn | Uttara Ashadha (¾), Shravana, Dhanishtha (½) |
| Kumbha | Aquarius | Dhanishtha (½), Shatabhisha, Purva Bhadrapada (¾) |
| Meena | Pisces | Purva Bhadrapada (¼), Uttara Bhadrapada, Revati |
3. How to Use This in Your Research
If you are matching an eclipse to an ancient text that says the eclipse occurred in Rohini Nakshatra:
- Enter Archeo-Astronomy Mode.
- Select the Ayanamsha used by that tradition (usually Lahiri for modern Indian Government references).
- Filter by Nakshatra: Rohini.
- The database will show only the eclipses where the Moon was within the 13.33° span of Rohini in the Lahiri system.
Tip: If the tradition you are referencing uses a non-Lahiri ayanamsha (e.g., Raman), the Nakshatra filter boundaries remain Lahiri-native, but the displayed Rasi and Nakshatra labels in the table will reflect your selected system. For most historical Indian references, the difference between systems is less than 2° — well within a single Nakshatra’s 13.33° span.
