A History of the Navigators Sextant
by Cotter, Charles H.-
pub by Brown Son and Ferguson Ltd, Glasgow, UK, 1983 -         - isbn 0-85174-427-3 - - 226 p. Total      
Notes and References after each chapter - - Acknowledgements p. v - - Authors Forward p. vi - - Index p. 225-226
    Charles H. Cotter, Master Mariner, PhD, Fellow of the Royal Inst. of Navigation, is indeed an expert in the history of navigation and especially the history of all instruments which were used to measure angles in marine navigation.
    The first period of rapid development of angle measuring devices came when European discoveries were beginning and the need for position finding became more serious due to more offshore (ocean crossing) voyages became common.
    I find it interesting that the second period of rapid development at the time when the search for Longitude was on and improved instruments were needed to make Lunar measurements. Measuring the location of the moon in the sky relative to highly visible stars can give the navigator time which is needed to accurately determine Longitude. Lunars were difficult to do, and the system worked, but using Harrisons chronometer was much easier.

1. Introduction.
2. The Genesis of the Mariners Angle-measuring Instruments
      -
3. Thw Seamans Quadrant
      - The tool Columbus used. It also used gravity to measure against. Difficult and next to impossible to use accurately at sea.
4. Mariners Astrolabe, Nautical Ring and Semicircle
      - The Mariners Astrolabe was the next instrument used. It also used gravity to measure against.
5. The Cross-Staff
      - The first instrument which measured the angle between the horizon and the object (star or sun) viewed.
      - I had no idea how many versions of Cross Staffs there were and how long they were used.
6. Shadow Staffs
      - To avoid being dazzled by the sun one turns ones back to the sun
      - and uses its shadow lined up with the horizon throgh a slit.
7. Early Instruments of Reflection
      - The beginning us using mirrors - pre-sextants
8, Improved Instruments of Reflection
      - Better pre-sextants
9. Improvements to Hadleys Quadrant
      - The developmen of the sextant as we know it.
10. Marine Sextants in the Twentieth Century
      - THe sextant developed as we know it.
11. Sextants for Coastal Navigation and Surveying
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12. Artificial Horizons for Marine Sextants
      - How to use a sextant when the horizon is not visible
13. Sextants for Air Navigation
      - A short chapter on the difficulties of using artificial horizons while flying.

It is a very thorough read. Very useful to really understand angle measurement finding tools.

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