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Nautical Astronomy: Past, Present and Future

Published online by Cambridge University Press:  01 October 1976

H. Cotter
H. Cotter
Affiliation:
(University of Wales Institute of Science and Technology)
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Extract

Chart, compass and log are the three fundamental instruments of navigation. It was not until mediaeval times, coinciding with the early development of these instruments, that navigation became scientific; and certain it is that without them the opening up of the oceans for exploration, as a preliminary to maritime trade, would have been delayed.

The defects of ‘dead reckoning’ navigation, the process by which a vessel's position may be pricked on a chart from compass and log observations, were of little consequence to medieval navigators whose activities were confined to the Mediterranean Sea and the coastal waters of Atlantic Europe. But following the advent of the Golden Age of Discoveries initiated by the Portuguese in the fifteenth century, when western Europeans first struck out to cross the Atlantic, the pressing need for a reliable method of checking DR positions led to the rise of nautical astronomy. The practice of this art which is secondary to the primary navigational aim of finding the way embraces the traditional methods of mathematical astronomy for ascertaining latitude and longitude. A nautical astronomer requires skill, mathematical and scientific expertise and certain indispensable equipment. A chart for pricking position as a preliminary to setting or rectifying a course, mathematical and astronomical tables to facilitate computations and instruments for measuring respectively altitudes and times; these are the main tools of nautical astronomy.

Information

Type
‘Two Centuries of Navigation’
Information
The Journal of Navigation , Volume 29 , Issue 4 , October 1976, pp. 334 - 341
Copyright
Copyright © The Royal Institute of Navigation 1976

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References

NOTES AND REFERENCES

1 Although it is wrong to suppose that early seamen ‘hugged the shore’ and were frightened to strike out into the open sea, the geography of maritime trade in mediaeval times meant that ships were never very far away from land; and navigators, therefore, found little or no difficulty in checking position from land observations when necessary.Google Scholar

2 I exclude the maritime activities of the Norsemen on the grounds that their techniques of navigation, although of great interest to maritime historians, did not influence the main stream of navigational progress.Google Scholar

3 Vide an interesting note by May, W. E. (1950). The double altitude problem. This Journal, 3, 416.Google Scholar

4 Cotter, C. H. (1972). Navigational Globes: Ancient and Modern. This Journal, 25, 345.Google Scholar

5 Davis described a variety of instruments for measuring the Sun's altitude in his The Seamans Secrets first published in London in 1595.Google Scholar

6 First suggested by Thomas Hood. (Vide Waters op. cit., p. 187).Google Scholar

7 A detailed account of the development of ‘shadow’ instruments for measuring altitudes is given in Waters, D. W. (1958). The Art of Navigation in England in Elizabethan and Early Stuart Times. London.Google Scholar

8 Hadley, J. (1731). The Description of a New Instrument for Taking Angles. Philosophical Transactions of the Royal Society. No. 425. London.Google Scholar

9 First suggested by Captain John Campbell R.N. in 1757.Google Scholar

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11 The best account of Harrison's work is given by Gould, R. T. (1923). The Marine Chronometer, its History and Development. London.Google Scholar

12 Gemma Frisius described the use of a timekeeper for finding longitude in his De principiis astronomiae et cosmographiae published in Antwerp in 1530. Johannes Werner proposed the lunar distance method in 1J14, and what appears to have been the earliest diagrammatic illustration of the method was given in Cosmographia Petri Apian by Gemma Frisius in 1524.Google Scholar

13 Detailed accounts of Mayer and his work have been given by Dr. E. G. Forbes. See, in particular, The Euler-Mayer Correspondence (1751–1755); a new perspective on eighteenthcentury developments in the lunar theory (1971). Also: Tobias Mayer's Lunar Tables. Annals of Science Vol. 22 (1966) pp. 1–25.Google Scholar

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19 Thomson, W. (1871). On the Determination of a Ship's Place from Observations of Altitude. Proceedings of the Royal Society of London. Vol. 19. See also: Cotter, C. H. (1972). Sir William Thomson and the intercept method. This Journal, 25, 91.Google Scholar

20 Saint-Hilaire, R. Marcq de Blond de (1875). Calcul du point observ´e. Revue Maritime et Coloniale. Vol. 46. Paris.Google Scholar

21 Vide Cotter, C. H. (1968). A History of Nautical Astronomy. London, pp. 293–308.Google Scholar

22 Vide Wimperis, H. E. (1920). A Primer of Air Navigation. London. In this early work on air navigation the author advocated a tabular adaptation of Nuñez' method for finding position by simultaneous star sights.Google Scholar

23 Particularly Sight Reduction Tables for Marine Navigation (in six volumes) H.O. 229/H.D. 605, described by D. H. Sadler as the tour de force of inspection tables for marine navigation.Google Scholar