Hobbies And Interests
Celestial Navigation
Astrolabes determined a celestial body's altitude and position, establishing the ship's location in relation to the latitude and time of day. Astrolabes were circular, with a rod to aim at the celestial body and a weighted string hanging from the center to measure the angle.
Cross-staffs were sticks with perpendicular crossbars of varying lengths, placed at prescribed distances along the staff. The celestial body's angle was found by sighting along the staff and discovering which crossbar fit the angle between the object and the horizon line.
Sextants measured the angle of celestial bodies compared to the horizon line (vertically) or other celestial bodies (horizontally). One object was sighted through the eyepiece and the angle found in relation to the second object by clamping a movable arm (sighting on the second object) to an arc with degree markings.
Navigation by Charting
Mariner's compasses have magnetized needles lined up with earth's magnetic fields, triggering one end to point toward the north pole. Compass points correspond to the chart's rose compass points.
Log Lines, knotted ropes with a log tied to one end and knots every nautical mile and one-tenth of a nautical mile, were tossed off the end of the ship while the knotted rope unraveled behind it. When the sand on a minute sand glass ran out, the rope was reeled back in and the knots counted to determine ship's speed in knots-per-minute.
Sandglasses (i.e. hourglasses) were flipped by the navigator as the sand ran out. Omission or failure to flip the sandglass would seriously affect navigational calculations, course plotting and the ability to determine the ship's position.
Navigating with Distance, Direction and Speed
Charts illustrate the earth's surface and waterways, including features like shoals, reefs and safe anchorages.
Latitude and longitude, parallels and meridians, poles and the equator were marked for determining location.
A rose compass illustrated the four cardinal directions (north, south, east and west) and the graduations in between (e.g. NNE, NE and ENE). Thirty-two compass points were represented.
Traverse boards kept track of the ships speed, distance and direction at hourly intervals, marked by pegs placed into specific holes. Watch officers compared the actual course (on the traverse board) to the course given by the captain.
Lead lines were ropes weighted on one end and knotted at precise distances, called fathoms. The weighted end was dropped into the water, establishing the depth by the number of knots entering the water, and was then compared with known water depths at specified chart locations.