The Journal · July 30, 2026

Privacy policy

This policy describes what SkyChart does with your data. It is written from the actual behaviour of the app rather than from a template, so it is specific — and where we send anything to a third party, we say which one and what exactly leaves your device.

Last updated: [[TO COMPLETE: date of publication]]. Data controller: [[TO COMPLETE: legal entity name, address, registration number]]. Privacy contact: [[TO COMPLETE: email address]].

What we collect, and why

Your account

When you create an account we store your email address, your first name, your interface language, and your password — never in clear text: it is hashed with scrypt, a function designed to be slow and memory-hard so that a stolen database is not a stolen list of passwords. If you sign in with Google or Facebook instead, we receive your email address and name from them and store no password at all.

Legal basis: performance of the contract between us. Without an account, the sky map cannot save your settings or your places.

Where you observe from

A sky map is useless without a location: what is above you depends entirely on where you stand. If you allow it, your browser gives us your coordinates, which stay on your device unless you save a place to your account. Saved places (a name, latitude, longitude and timezone) are stored so that the app opens on the right sky on your next visit.

You can refuse geolocation and still use everything: pick a city by hand instead. Nothing degrades except the convenience.

Notifications

If you turn on notifications, we store the technical address your browser gives us for delivery, its two encryption keys, your coordinates and timezone — needed to work out when the International Space Station will actually pass over you and at what local time — and which categories of alert you asked for. We keep a short record of what we have already sent you, so the same event is never announced twice.

Legal basis: your consent. Turning notifications off deletes the subscription. If your browser tells us an address is dead, we delete it without being asked.

Payments

Premium subscriptions are handled by Stripe. Your card number never reaches our servers and we could not see it if we wanted to. We keep the customer and subscription identifiers Stripe gives us, and the status and end date of your subscription — that is what tells the app whether to unlock premium features.

What leaves your device, and to whom

• Weather forecasts. Observing conditions come from Open-Meteo. The request goes through our server rather than straight from your browser, so Open-Meteo never sees your IP address, and the coordinates we forward are rounded before being sent.
• Satellite orbits. Orbital data comes from CelesTrak. These requests carry no information about you at all — the same data is fetched for everybody and cached on our side.
• Map tiles. The light-planning map loads tiles from OpenStreetMap, CARTO and Esri. Those providers see the requests for the map squares you look at.
• Transactional email. Account confirmations, password resets and billing notices are sent through Brevo. They process your email address on our behalf.
• Payments. Stripe, as described above.

We do not sell your data, we do not share it with advertisers, and we do not build advertising profiles.

What stays on your device

A good deal, deliberately. Your display settings, your compass calibration and the location it was measured at, the accuracy last reported by your phone's magnetometer, and any manual correction you make to the light-pollution estimate are all kept in your browser's local storage. They never reach us. Clearing your browser data resets them.

The sky map itself computes everything locally: positions of the planets, rise and set times, satellite passes. Your location is not sent anywhere to be turned into a star chart.

Cookies

We use two, both strictly functional: one holds your signed session so you stay logged in, and one remembers your chosen language. Neither tracks you across other sites. Analytics, if enabled, is described on the cookie page.

How long we keep things

• Your account and its settings: until you delete it. Deletion is immediate and irreversible.
• Notification subscriptions: until you turn notifications off, or until your browser reports the address as invalid.
• Billing records: as long as accounting law requires us to keep them, independently of your account.
• Email verification and password-reset tokens: a few hours, and stored hashed — a leak of our database would not let anyone reset your password.

Your rights

Under the GDPR you can ask for a copy of your data, correct it, have it erased, take it elsewhere in a portable format, object to a particular use, or withdraw a consent you previously gave. Write to [[TO COMPLETE: privacy contact email]] and we will answer within one month.

You can delete your account yourself from your account page — no email, no waiting, no retention period. If you believe we have mishandled your data, you may complain to your national data protection authority; in France that is the CNIL.

Children

SkyChart is suitable for all ages, but an account requires you to be at least [[TO COMPLETE: minimum age, 15 in France, 16 in several EU states]]. Below that age, a parent or guardian must create and manage the account.

Changes

If we change how we handle your data in a way that matters, we will tell you before it takes effect — by email if you have an account. The date at the top of this page always reflects the current version.