ca. 9th century A.D.: First astronomical quadrant
9th century A.D.: First astronomical astrolabe. Brass and/or wood
10th century A.D.: Earliest surviving example of astronomical
astrolabe
11th century A.D. Directional properties of lodestone employed
1187: Earliest known description of the compass
1342: Cross staff described by Levi ben Gerson
1415: Prince Henry the Navigator establishes his navigation
institute
ca. 1450: First recorded mention of the mariner's simple
quadrant, although the instrument predates this period
ca. 1460: First mariner's astrolabe. Sheet brass construction
ca. 1500: Introduction of cast brass mariner's astrolabe
1555: Earliest surviving example of a dated mariner's astrolabe
1594: Captain John Davis introduces backstaff
1631: Pierre Vernier describes his method for making an improved
scale reading
17th century: Backstaff constructed of walnut, lignum-vitae, and
fruitwood. In-line scale.
18th century: Backstaff constructed of ebony, rosewood, and
mahogany in addition to earlier materials. Diagonal scale.
1731: John Hadley introduces reflecting quadrant
1735: John Harrison's first chronometer
1756: Mayer's reflecting circle
1757: First "Hadley sextant" by John Bird. Brass, ebony
and ivory introduced as materials for constructing instruments.
Brass begins replacing wood as the preferred material, starting
with the index arm in quadrants
1768: Scale dividing engine by Jesse Ramsden
ca. 1770: Finite scale on vernier calibrated "20 - 0 -
20".
Earlier instruments calibrated "10 - 0 - 10"
ca. 1780:Instruments decrease in size with widespread use of
dividing engine in scale manufacture
ca. 1820: Elimination of backsight feature in the construction of
most octants
ca. 1840: Octants and sextants more similar in appearance with
the inclusion of handles, optics, and all-brass construction in
octants
ca. 1880: Cessation of the production of wooden instruments of
the navigational type
ca. 1918: Inclusion of the drum micrometer feature in modern
sextants
ca. 1940: Ball recording sextant, aircraft sextant