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Celestial Navigation in Twelve Evenings
A short course as a composed site: twelve dated lessons in three parts, each with a quiz checked in the page, your progress kept in your own browser and nowhere else.
Part one: the sky and the instrument
| Evening | Lesson | What it covers |
|---|---|---|
| The celestial sphere | Declination and hour angle: the sky's own latitude and longitude. | |
| The sextant | Reading the arc and the drum, and the errors you check each time. | |
| Time and the almanac | Why a second matters, and how the daily pages are read. | |
| Correcting the altitude | From the sextant reading to the observed altitude: index error, dip, refraction, semi-diameter. |
Part two: sights and their reduction
| Evening | Lesson | What it covers |
|---|---|---|
| The noon sight | Latitude from the Sun's meridian passage, in one line of arithmetic. | |
| Latitude by Polaris | The pole star's altitude, corrected for its small circle, is your latitude. | |
| The navigational stars | Fifty-seven stars, how to find them at twilight, and which to choose. | |
| The intercept method | An assumed position, a computed altitude, and the intercept towards or away. |
Part three: the day's work
| Evening | Lesson | What it covers |
|---|---|---|
| Plotting the position line | The plotting sheet, the assumed position and the line that is not a point. | |
| The running fix | Carrying a morning Sun line forward to noon, by the log and the course. | |
| The Moon and the planets | Daylight sights of the Moon, the planets at twilight; parallax and the extra corrections. | |
| The day's work | A passage day from star twilight to star twilight, as the navigator keeps it. |
A demonstration: the course, its tutor and its loft are invented; the navigation is real. Built by plinth from EDN and Markdown; the quizzes are checked in the page and send nothing, and the only thing kept is your progress, in your own browser.