# Asterodos: learn celestial navigation A course in celestial navigation # Find your position from the sky Thirteen short modules and an optional warm-up, from a noon latitude to a three-star fix. Already know a topic? Open it and solve one problem to skip ahead. ## Foundations - [Start hereLatitude and the nautical mile (optional)Read a latitude, turn a difference in latitude into miles, and keep a dead reckoning position.](https://asterodos.com/m/onramp)Not started - [Angles, time and UTConvert between arc and time, and turn zone time into UT.](https://asterodos.com/m/time)Not started - [Where the Sun is: GHA and declinationRead the Sun's GHA and declination from the almanac for any second of UT.](https://asterodos.com/m/almanac)Not started - [Sextant corrections: Hs to HoTurn a sextant reading into the observed altitude, in the right order.](https://asterodos.com/m/sextant)Not started ## First sights - [Latitude from the noon SunKnow when noon is by your watch, and work a complete noon sight for your latitude.](https://asterodos.com/m/noon)Not started - [Checking the compass by the SunFind the compass error and deviation from the Sun's bearing at sunrise or sunset.](https://asterodos.com/m/compass)Not started - [Latitude from PolarisFind your latitude at twilight from the Pole Star, with the Polaris tables.](https://asterodos.com/m/polaris)Not started ## The line of position - [The circle of equal altitudePlace a body's ground position, and turn one altitude into a circle of position in miles.](https://asterodos.com/m/circle)Not started - [The line of positionTurn Ho and Hc into a line of position, and plot it from your DR.](https://asterodos.com/m/lop)Not started - [The assumed position and LHAChoose the assumed position the tables need, and find LHA for any body.](https://asterodos.com/m/ap)Not started - [The intercept methodReduce a Sun sight with Pub. 249 or by formula on a calculator: Hc, Zn and the intercept.](https://asterodos.com/m/intercept)Not started ## The fix - [Planning a twilight fixFind the time of twilight by your watch, and choose stars that give a good fix.](https://asterodos.com/m/planning)Not started - [The fixPlot two or more lines of position, including a running fix, and judge the fix.](https://asterodos.com/m/fix)Not started - [Planets and the MoonReduce planet sights at twilight, and (advanced) a Moon sight for a daytime fix with the Sun.](https://asterodos.com/m/planets)Not started ## Your sky Every module you finish lights a star. The Big Dipper comes first; its two pointers lead you to Polaris, the last star of the course. 0 of 14 stars lit Stars are shot in twilight, while the horizon is still sharp. Give a position to see when tonight’s window opens where you are. It stays on this device. ## Before you start: a concept quiz 12 quick questions on the ideas people most often get wrong. Take it now and again at the end, and see what changed. ## Final assessment Five full sights from the watch and sextant, no hints, never seen in practice. Pass by putting the boat within 5 nm on four of them. ## Passages: a day at sea Put it all together. Navigate a whole day of an ocean passage with no GPS, from the morning Sun line to the evening star fix. Every voyage is different, so sail them as often as you like. - [**San Diego to Hilo**](https://asterodos.com/passage/hilo)A day in the trade winds with no GPS: a Sun line, the noon sight, a running fix, the current, a compass check and a star fix. - [**Canaries to Antigua**](https://asterodos.com/passage/antigua)The Atlantic crossing's last week: a dawn star fix and Polaris, the compass at sunrise, a running fix at noon and a planet at dusk. - [**Newport to Bermuda**](https://asterodos.com/passage/bermuda)The Gulf Stream: find the current from two fixes, work the course to steer across it, and check it with the evening stars. - [**Panama to the Galápagos**](https://asterodos.com/passage/galapagos)Crossing the equator: a noon latitude a few miles north of the line, Polaris gone, and a star fix that says south. - [**Tahiti to Fiji**](https://asterodos.com/passage/fiji)Southern stars and the Sun to the north, and the date line: lose a day on the ship's calendar between noon and twilight. - [**Azores to Falmouth**](https://asterodos.com/passage/falmouth)Northern waters in June: a Sun–Moon fix by day and the long northern twilight before the star fix. ## Tools - [**Work your own sight**Took a real sight? Reduce it step by step and plot your fix.](https://asterodos.com/sight) - [**Sight reduction calculator**Hc, Zn and the intercept from your DR, GHA and declination, every step shown.](https://asterodos.com/sight-reduction-calculator) - [**More free tools**Noon sight and Polaris calculators, a Sun almanac and a star finder.](https://asterodos.com/tools) - [**Guides**Where to start, how to use a sextant, the intercept method, and more.](https://asterodos.com/guides) - [**Celestial sphere explorer**Turn the sky's sphere and see what each term means on it.](https://asterodos.com/sphere) - [**The real books: Pub. 249 and Bowditch**How to read the printed tables and find your way around Bowditch.](https://asterodos.com/books) - [**Sights on land**No sea? Use an artificial horizon, and practice from your backyard.](https://asterodos.com/land) - [**Printable forms**A sight reduction form and a plotting sheet, for paper and pencil.](https://asterodos.com/print) - [**Concept quiz**Twelve questions on the commonest misconceptions, before and after the course.](https://asterodos.com/quiz) - [**Glossary**Every term in the course, linked to where it is taught.](https://asterodos.com/glossary) --- From Asterodos, a free interactive course in celestial navigation: https://asterodos.com/ For learning, not for navigating a vessel.