Course / Terms of use

Terms of use

Last updated October 20, 2026

This is a course for learning celestial navigation, not a navigation tool. Never rely on it, or on anything worked out with it, for the safety of a vessel or anyone aboard.

What the course is

Asterodos teaches the theory and practice of finding a position from the Sun, Moon, planets and stars. Its almanac is computed from the JPL DE440 ephemeris and its sight reduction tables are computed in the style of Pub. 249. They are made for teaching: they are not the official Nautical Almanac or sight reduction tables, and they may contain errors. At sea, use the official publications, and check every position by other means.

No warranty

The course is provided “as is”, without any warranty that it is accurate, complete, available or free of errors. To the fullest extent the law allows, the Asterodos team is not liable for any loss or damage arising from using it or relying on it. Nothing here limits any right you have that the law does not allow to be limited.

Using the course

You may use the course for your own learning, and print its forms for your own use. Please do not copy, republish or sell its lessons, problems, pictures or code. Sailing schools and instructors who would like to use it with students are welcome to get in touch.

The beta

The course is free while it is in beta, and it may change as it improves. If parts of it later become paid, that will be announced here first.

Changes

These terms may be updated; the date at the top shows when. Using the course after a change means you accept the new terms.

Contact

For any question about these terms, contact the team at hello@asterodos.com, or use the feedback page.