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Octant (instrument)
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The octant, also called a reflecting quadrant, is a reflecting instrument used in navigation.
Octant. This instrument, labelled Crichton - London, Sold by J Berry, Aberdeen, appears to have an ebony frame with ivory scale, vernier and signature plate. The index arm and mirror supports are brass. Rather than use a sighting telescope, this instrument has a sighting pinnula.
Octant. This instrument, labelled Crichton - London, Sold by J Berry, Aberdeen, appears to have an ebony frame with ivory scale, vernier and signature
Octant reverse side. This side is not seen in photographs very often. On the right, the thumbscrew to adjust the horizon mirror can be seen. At the to
Octant reverse side. This side is not seen in photographs very often. On the right, the thumbscrew to adjust the horizon mirror can be seen. At the top, one of the feet on which the octant rests in its case is just below the index arm axis. On the left the notepad is clearly visible. This small keystone-shaped piece of ivory, scarcely larger than a thumbnail, was used by the navigator to record his readings.
Details on an octant. This photo shows the graduated scale and the end of the index arm with the vernier. The thumbscrew used to lock the index arm po
Details on an octant. This photo shows the graduated scale and the end of the index arm with the vernier. The thumbscrew used to lock the index arm position is seen below the index arm while the thumbscrew used for fine adjustment of the arm is on the left. To the right of the value 50 on the main scale, the SBR logo is engraved. The scale is directly graduated in degrees and thirds of a degree (20'). The vernier can divide the 20' intervals to the nearest minute of arc.
Octant details showing the double-holed sighting pinnula. Also visible is the small cover that can block one or the other of the holes. The horizon mi
Octant details showing the double-holed sighting pinnula. Also visible is the small cover that can block one or the other of the holes. The horizon mirror is on the opposite side of the instrument. The left side is transparent while the tin amalgam on the mirrored side has completely corroded and no longer reflects light. The back of the index mirror's holder is at the top and the three circular glass shades in square frames are between the two mirrors.
Isaac Newton
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Sir Isaac Newton was an English polymath who was a mathematician, physicist, astronomer, alchemist, theologian, author and inventor. He was a key figure in the Scientific Revolution and the Enlightenm
Octant (instrument)
…observer and, in doing so, doubles the angle measured. This allows the instrument to use a one-eighth of a turn to measure a quarter-turn or quadrant. Isaac Newton presented his reflecting quadrant to the Royal Society in 1699. Newton's design for the instrument was probably built as early as 1677. A detailed…
Portrait of Isaac Newton, 1689
Portrait of Isaac Newton, 1689
Some of the figures added by Isaac Newton in his 1672 and 1681 editions of the Geographia Generalis. These figures appeared in subsequent editions as
Some of the figures added by Isaac Newton in his 1672 and 1681 editions of the Geographia Generalis. These figures appeared in subsequent editions as well.
Newton in 1702 by Godfrey Kneller
Newton in 1702 by Godfrey Kneller
A replica of the reflecting telescope Newton presented to the Royal Society in 1672 (the first one he made in 1668 was loaned to an instrument maker b
A replica of the reflecting telescope Newton presented to the Royal Society in 1672 (the first one he made in 1668 was loaned to an instrument maker but there is no further record of what happened to it).