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Product

Change of Chart

A personal astrocartography map that calculates entirely in the browser — no backend, no signup. Enter your birth details and see where each planet was rising, setting, or at its highest point around the world, explained in plain language instead of ephemeris data.

Status
In beta
Built with
Vanilla JavaScript, HTML5, CSS3
Tagline
Where your planets touch the ground.
Welcome screen inviting visitors to enter their birth details
A blank slate — no data shown until you enter your own.

The problem

Most astrocartography tools read like a spreadsheet — accurate, but cold, and usually gated behind an account or a paid API. The goal was a tool that actually explains what a planetary line means and why it matters, calculates a real, historically-accurate birth chart (including proper timezone handling), and does all of it without collecting a single piece of user data.

What we built

A from-scratch client-side ephemeris engine, ported from Keplerian orbital elements into vanilla JavaScript and validated against Swiss Ephemeris to within a fraction of a degree. It computes all ten planetary lines, a natal Sun/Moon/Rising reading, and a two-location comparison tool with a synthesized verdict — all running locally in the visitor's browser, with real historical DST-aware timezone resolution via the Intl API.

How it works

  • Client-side ephemeris engine

    Full birth chart calculated in-browser from Keplerian orbital elements — validated against Swiss Ephemeris.

  • 10 planets, 4 lines each

    Ascendant, Descendant, Midheaven, and Imum Coeli lines for every planet, plotted on an interactive world map.

  • Plain-language interpretations

    Every line explained in a sentence or two, with a proximity-ranked, explained list of nearby cities.

  • Goal-based filtering

    Filter lines by career, love, adventure, or home to surface what actually matters.

  • Sun / Moon / Rising panel

    A real natal-chart reading computed for the exact birth moment and location.

  • Compare two places

    Side-by-side comparison of any two cities with a synthesized verdict on which aligns more strongly.

  • Automatic timezone resolution

    Historical, DST-aware UTC offset resolved automatically from birthplace via the browser's Intl API.

  • Shareable charts

    Generates a URL that reopens directly into a specific birth chart.

Development journey

Started as a straightforward astrocartography visualizer and grew into a from-scratch orbital mechanics engine after deciding a server-side dependency wasn't acceptable for a portfolio piece. The biggest technical hurdle was a subtle epoch bug that threw the Moon's position off by 19 degrees — traced by cross-validating every planetary position against Swiss Ephemeris until they matched to a fraction of a degree.

What's next

  • Shipped

    Public launch

    Live at your Netlify URL, calculating real birth charts entirely client-side.

  • Now

    Continuous refinement

    Ongoing polish on interpretations, city coverage, and accessibility.

  • Next

    Save & revisit charts

    Let visitors bookmark or return to a previously generated chart.

Selected views

Birth details form with automatic timezone detection
Pick a city and the timezone resolves itself.
Recommended planetary lines panel with nearby cities
Click any line to see what it means and what's nearby.
Compare Two Places tool showing planetary lines for two cities
Compare any two places side by side, with a synthesized verdict.