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‘Columbus's Method of Determining Longitude’

Published online by Cambridge University Press:  23 November 2009

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I am pleased to see that, in light of my critical evaluation, Arne B. Molander has reevaluated a number of points in his analysis, and has revised his proposals of Columbus's alleged use of the Moon for determining his longitude. However, it is disappointing that these latest proposals again do not seem to have been thoroughly considered.

Since it is clear that Columbus's East–West position fixes are not correlated with visible lunar-planetary conjunctions, Mr Molander's latest hypothesis is that Columbus observed a dark-horizon moonrise or moonset near each conjunction – which usually can be done whether or not the conjunction itself is visible. However, it is entirely unclear how such an observation can be converted into a longitude. Reading attentively, we can glean a few details of this process: only a single observation is required, since some positions are computed within a few hours of the purported observation; and Columbus apparently used the Ephemerides of Johann Miiller, since errors in that ephemeris are alleged to have caused errors in the computed longitude. In his 1992 paper, Mr Molander asserted that timing of the conjunction is not required by this method, because Columbus somehow utilizes the Moon's daily topocentric motion. But how this datum is utilized, and in fact all details of the longitude determination itself, are entirely obscure.

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Forum
Copyright
Copyright © The Royal Institute of Navigation 1997

References

REFERENCES

1Molander, Arne B. (1996). ‘Columbus's method of determining longitude’. This Journal, 49, 444.Google Scholar
2Pickering, Keith A. (1996). Columbus's method of determining longitude: an analytical view. This Journal 45, 101103.Google Scholar
3Molander, Arne B. (1992). Columbus and the method of lunar distance. Terrae Incognitae 24, 6869.CrossRefGoogle Scholar
4Randies, W. G. L. (1995). Spanish and Portuguese attempts to determine longitude in the fifteenth and sixteenth centuries. The Mariner's Mirror 81:4403.Google Scholar
5Kelley, James E. Jr (1983). In the wake of Columbus on a portolan chart. Terrae Incognitae 15, 102104.CrossRefGoogle Scholar
6Pickering, Keith A. (1996) Columbus's method of determining longitude: an analytical view. This Journal, 49, 109.Google Scholar