SidereoTerms of Use
Last updated 2 September 2026
Sidereo is an iPhone app made by Helder Pereira. Using it is governed by Apple's standard licence for apps bought through the App Store — the Licensed Application End User License Agreement. These terms add the details specific to Sidereo; where the two disagree, Apple's agreement wins.
What the app is
An astronomy and astrophotography instrument. It computes positions on your device from published models — Meeus' series for the Sun and Moon, Keplerian elements for the planets, an SGP4 propagator for satellites — and works with no network connection.
Those computations are accurate enough to find things in the sky and to plan a photograph. They are not suitable for navigation, for any safety-critical purpose, or for any decision where being wrong carries a cost. Weather and sky-quality figures are forecasts and estimates from third-party data, and the app labels them as such.
Subscriptions
Sidereo is free to use. Sidereo Pro is an optional auto-renewing subscription, offered monthly and yearly, and a one-time lifetime purchase. Prices are shown in your local currency inside the app before you buy, and the app names exactly what Pro unlocks.
- Payment is charged to your Apple Account at confirmation of purchase.
- A subscription renews automatically unless it is cancelled at least 24 hours before the end of the current period, and your account is charged for renewal within 24 hours of the end of that period.
- You can manage or cancel a subscription at any time in your Apple Account settings. Cancelling stops the next renewal; it does not refund the period already paid for.
- Purchases are handled entirely by Apple through StoreKit. We never see or store your payment details, and refunds are Apple's to give — request one through Apple Support.
Your data
There are no accounts. Everything you create in the app — favourites, observation logs, discovered objects, gear — is stored on your device and deleted with the app. The privacy policy lists every request that leaves your phone and what each one receives.
Other people's work
Star positions come from the Yale Bright Star Catalog (Hoffleit & Warren, 1991, public domain). Orbital elements come from CelesTrak and the Minor Planet Center. Object summaries shown in the app are fetched from Wikipedia and remain under CC BY-SA 4.0. The app bundles IBM Plex Mono under the SIL Open Font License 1.1; the full text ships inside the app under Settings → Licenses. Music in the app is by Helder Pereira and is licensed for use in Sidereo only.
Images you create with the app are yours. Sidereo claims nothing in them.
What we do not promise
The app is provided as it is. It is not guaranteed to be uninterrupted or error-free, and the optional network features depend on services we do not control and which can change or stop. To the extent the law allows, we are not liable for loss arising from use of the app; nothing here limits rights you have under the consumer law of your own country, which for readers in the EU includes rights that cannot be signed away.
Changes
If these terms change, the date at the top of this page changes with it and the previous version is replaced here.