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Narratives

Lunar Cartography

Cassini's Carte de la Lune (Inv 13579 is an eighteenth century reduction of the 1679 original) is sometimes cited as the first scientific mapping of the moon, but it sits within an emerging tradition of lunar cartography with varying levels of accuracy and detail.


In the solar system the moon is uniquely close enough for relatively detailed terrestrial observation of its topographical features, both with the naked eye and through a telescope. Most early images were allegorical, and many cultures have their own perceived images created from the surface shadows connected with legend and folklore, ranging from the man in the moon, to the Chinese vision of a rabbit sat on its haunches pounding rice. The images it is possible to visualise alter due to the varying angle of orientation.


The first image of the moon to be usefully termed a map is William Gilbert's (c1544-1603) naked-eye view of the moon with nomenclature. Gilbert adhered to a Copernican philosophy of the planet and produced De Magnete with the aim of supporting the theory. Gilbert's ideas on magnetism were more fully explored in De Mundo, a work which included his map of the moon, (which he believed, along with the earth, was magnetic). His theories on the magnetism of the earth and moon, being drawn into Copernican orbit, and his ideas of the tides on earth being caused by the magnetic pull of the moon prefigured Newton's theory of gravity. Gilbert lamented the lack of useful images of the moon from antiquity preventing the opportunity of discovering any major visible changes.


Galileo's Siderius Nuncius 1610 included the first published telescopic maps of the moon (Thomas Harriot (1560-1621) created the first telescopic sketch). Its wide circulation enhanced the influence of the belief that the dark spots on the moon's surface were seas (as opposed to the opposite; a theory adhered to by Gilbert, Da Vinci and initially, Kepler).


The 1645 map by Van Langren (Langrenus) is often seen as the first real map of the moon which shows the topography and surface shading of the moon and also introduced the nomenclature of the moon, some of which is still used today.


In his Micrographia Robert Hooke published the first depiction of a single feature of the moon, the Hipparchus crater, created using a 30ft telescope. When compared with a modern photograph, Hooke's image is remarkably accurate.


The map created by Cassini, 1680, was more detailed than its predecessors, completed using a larger and more unwieldy telescope, but the accuracy is poorer and it was originally published without any nomenclature. Nevertheless, the engraving work by Parigny has been praised and the map is aesthetically appealing. It follows the convention of oblique illumination (meaning the topographical features are most defined and prominent) and uses 'south up' orientation, achieved by using a positive (convex) eye-piece. The potential significance of the map's production was lessened due to restrictions in production and distribution.  A smaller image was published in 1692 in advance of the predicted lunar eclipse in July of that year. The aim was to be able to gain accurate longitude values by measuring the length of time it took for certain spots to be covered by the earth's shadow.


The end of the eighteenth century brought more refined methods for constructing reflecting telescopes with William Herschel's design for a large aperture and short focal length. In 1775 Tobias Mayer produced the first map based on measured points.


The nineteenth century produced four major lunar maps; Wilhelm Lohrmann 1824, W. Beer and J.H. von Mädler 1834, Edmund Neison (Edmund Neville Nevill) 1876, J.F. Julius Schmidt 1878, and marked the end of pre-photographic lunar cartography. The emergence of photography meant that professional astronomers focused their attention on more challenging phenomena such as stars, nebulae and galaxies, and lunar cartography became largely an amateur enthusiasm.

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