Terms of Use for Nightglass

Nightglass: Stargazing Plan Published by OFO Labs

Last Updated: August 2026

Please read these Terms of Use carefully before using Nightglass. By downloading or using the app, you agree to these terms.

Acceptance of Terms

By accessing or using Nightglass, developed and published by OFO Labs, you agree to be bound by these Terms of Use. If you do not agree, do not use the app.

The App

Nightglass works out what is worth observing in the night sky from your location, ranks it, and tells you the window for each object. Everything is computed on your device from orbital mechanics and a bundled catalogue. It makes no network requests.

What We Promise About the Astronomy

We think this belongs in the terms rather than only in the marketing.

The positions Nightglass computes come from standard published algorithms: the solar and lunar theories in Meeus, Astronomical Algorithms, and NASA JPL's approximate Keplerian elements for the planets. They are checked in our test suite against the worked examples in those references.

That accuracy is far more than enough to answer the questions this app asks: whether an object is above your horizon, how high it gets, and when. It is not intended for telescope pointing, navigation, timing an occultation, or any purpose where being wrong by an arcminute matters. Do not use Nightglass for navigation or for any safety-critical purpose.

Observing conditions depend on weather, light pollution, local horizon obstructions and your equipment, none of which Nightglass knows about. A high score means the geometry is good, not that you will definitely see something.

Nightglass Pro

Tonight's plan is available to everyone, in full, permanently: the complete ranked list, the Moon, every naked-eye planet, the eighteen brightest stars and eight showpiece objects.

Nightglass Pro is a one-time purchase, not a subscription. It adds planning for any night in the next two weeks, the best-nights ranking for your site, the complete 110 object Messier catalogue, and the life list.

Purchases are processed by Apple and are subject to Apple's terms. Refunds are handled by Apple, not by us. If you delete and reinstall the app, or install it on another device using the same Apple Account, use the Restore option on the paywall to recover your purchase.

Your Content

Observing sites you save and objects you mark as seen are stored on your device and belong to you. We never receive them and cannot recover them for you if you delete the app.

Acceptable Use

Nightglass is for personal use. Do not attempt to reverse engineer, redistribute, or resell the app or its bundled catalogue.

Disclaimer

Nightglass is provided "as is", without warranty of any kind. To the fullest extent permitted by law, OFO Labs is not liable for any loss arising from the use of this app.

Changes to These Terms

We may update these terms. The current version always appears on this page with the date it was last updated.

Contact

Questions about these terms can go to ofolabs@gmail.com.