Privacy and legal
Who is responsible
This site and the Siderarium app are published by Hippocrene Design Works LLC, which is the data controller for the purposes of the EU General Data Protection Regulation (GDPR) and comparable laws.
What the app does with your data
- Nothing leaves your device. The app computes the sky in your browser. Your settings, your birth data (date, time and place) and your saved charts are kept in the browser's local storage on your device. They are never transmitted to us or to anyone else.
- No cookies. The site and the app set no cookies. Local storage is used only for the settings you choose, which is strictly necessary for the app to remember them; for this reason no consent banner is shown.
- No analytics, no trackers, no third-party requests. The fonts are served with the app rather than from a font service.
- Location. The "here" button asks your browser for your position so that the horizon of the dial can be your own. The browser asks your permission first; the coordinates are used on the device only and can be cleared by choosing a city instead.
Hosting
The site and the app are served by GitHub Pages. GitHub may log visitor IP addresses to operate the service and meet its legal obligations, under the GitHub General Privacy Statement. We do not receive these logs.
Your rights
Because we hold no personal data about you, there is nothing for us to access, correct or delete on our side; everything the app knows about you is on your device and under your control. If you have a question under the GDPR you can write to Hippocrene Design Works LLC. You also have the right to lodge a complaint with your supervisory authority.
Copyright and proprietary notice
Siderarium, its name, mark, dial, design, rules and method are proprietary. © 2026 Hippocrene Design Works LLC. All rights reserved. Every image exported from the app carries this notice. The ephemeris is computed with Astronomy Engine (MIT licence, Don Cross); the typefaces Geist and Geist Mono are used under the SIL Open Font License; the place names, coordinates and time zones offered by the birthplace search come from GeoNames (CC BY 4.0, geonames.org) and are bundled with the app, so no search leaves your device.
Changes
This notice will be updated when the service changes; the date above is the date of the current version.