A private, offline-capable chart calculator for Hellenistic, Vedic, and medieval traditions — installable on any device, with all data stored locally on yours.
Back up your saved charts as a JSON file. Files are local only — keep your own copy somewhere safe (cloud storage, email to yourself, etc.).
AsterTel is built around a simple principle: your birth data is nobody's business but yours. There is no account, no login, no server owned by this app that stores what you enter.
All of the above live in your browser's localStorage. Clearing browser data removes them.
AsterTel makes three kinds of outbound requests, only when you trigger them:
Your name, your chart type, and any other personal context are never transmitted.
If you tap 📍 Current location, the browser will ask for permission to share your coordinates with this app. Those coordinates are used locally and never transmitted except as part of the timezone lookup above (if you allow it). You can deny permission and enter coordinates manually.
After your first successful load, the app continues to work offline — you just can't use the Look Up place search, the Guess Offset button, or 📍 Current location without a connection. Manual entry still works and will produce exactly the same charts.
The final page of every exported PDF contains a text prompt suitable for pasting into an AI assistant for chart interpretation. The prompt includes your chart's calculated data. If you subsequently paste that prompt into ChatGPT, Claude, Gemini, or any other LLM, that service's data-handling policy applies — not this app's. Do not paste the prompt into a service you don't trust with birth data.
This page documents the assumptions, tools, and precision limits behind every chart AsterTel produces. Where accuracy matters — rectification, legal timing, serious electional work — always cross-reference a Swiss Ephemeris implementation.
All planetary positions, including the Sun, Moon, classical planets, and nodal axis (Rahu/Ketu via lunar-node calculation), are computed by astronomy-engine (v2.1.19, MIT-licensed, pure JS). This library implements the JPL ephemeris equivalents and is accurate to roughly arc-second precision from 1700 to 2200 AD.
Swiss Ephemeris (SWISSEPH) is the gold standard for professional astrology and covers a wider date range with slightly higher precision for deep-historical charts, but it is not available as a pure-JS client-side library. For charts before ~1700 or after ~2200, AsterTel's output becomes less reliable.
Vedic positions use the Lahiri ayanamsa (the official government-of-India precession convention), computed at the moment of the chart. Other ayanamsas (Krishnamurti, Fagan-Bradley, Raman, etc.) are not supported. If your tradition uses a different ayanamsa, your sidereal positions will differ from AsterTel's by 1–5 arc-minutes.
Six house systems are implemented:
Placidus and Koch automatically fall back to Porphyry above ±66.56° latitude, with a visible warning explaining why.
The Western wheel shows two concentric rings of minor dignity inside the zodiac band:
These are two different traditional schemes — terms are unequal and triplicity-derived, decans are equal and Chaldean-ordered. They are not alternative versions of the same thing.
The default is traditional / classical: Mars rules Aries and Scorpio, Saturn rules Capricorn and Aquarius, Jupiter rules Sagittarius and Pisces. The Sun rules Leo, Moon rules Cancer. A toggle (next to the house selector) enables modern rulers (Uranus → Aquarius, Neptune → Pisces, Pluto → Scorpio), which are then shown alongside traditional rulers in the Rulers card and on the Western wheel. Dispositor analysis always uses traditional rulers regardless of the toggle — modern rulers dissolve the dual-rulership structure that lets dispositor chains resolve.
All 15 classical vargas (D1, D2, D3, D4, D7, D9, D10, D12, D16, D20, D24, D27, D30, D40, D45, D60) are computed using the Jagannatha Hora conventions. Each varga Lagna is derived from the sidereal positions, not tropical.
Natal aspect lines use classical Ptolemaic orbs (conjunction 8°, opposition 8°, trine 7°, square 7°, sextile 5°). Transit→natal aspects use tighter orbs (2° for majors, 1.5° for sextiles) to filter signal from noise. No harmonic or minor aspects are displayed.
For an accurately recorded birth time (to the minute), AsterTel's positions are typically within a few arc-seconds of Swiss Ephemeris. House cusps for quadrant systems are iterative and converge to arc-second precision. But:
Choose a moment and location to compute the planetary day ruler, current hour, and full 24-hour table.
A private, offline-capable chart calculator for Hellenistic, Vedic, and medieval astrology — installable on any device, with all data stored locally on yours.
Your birth data lives in localStorage on this
device. No account, no sync, no analytics. External requests
only when you trigger them (place lookup, timezone lookup, CDN
assets). See for specifics.
If you load AsterTel in Chrome on Android, a hint will appear offering to install the app to your home screen. Installed, it runs offline, launches from an icon, and respects your device's system theme. You can install from iOS Safari's share-sheet by choosing "Add to Home Screen."
Built with astronomy-engine, Google Fonts (Cinzel, Cormorant Garamond, JetBrains Mono), and no framework. Place lookup via OpenStreetMap Nominatim; timezone lookup via timeapi.io.