The So-Called ‘Chaucer Astrolabe’ from the Koelliker Collection, Milan

An Account of the Instrument and Its Place in the Tradition of Chaucer-Type Astrolabes

in Nuncius
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The so-called “Chaucer Astrolabe” from the Koelliker collection, Milan, is a remarkable 14th-century English instrument. In addition to recounting its recent story and expounding its detailed description, this article offers a multi-sided approach to the object. The instrument is examined in relation to some of the early manuscript copies and to other astrolabes that have most commonly been seen as linked to Geoffrey Chaucer’s Treatise on the Astrolabe. In particular, the article provides stylistic and astronomical analyses through comparisons with the illustrations in the early copies of the Treatise, a selection of very similar instruments, and the data of the Pseudo-Messahalla star table. This multi-sided approach has some implications for existing scholarship on the astrolabes in the Chaucer tradition.

The So-Called ‘Chaucer Astrolabe’ from the Koelliker Collection, Milan

An Account of the Instrument and Its Place in the Tradition of Chaucer-Type Astrolabes

in Nuncius




Mara Miniati“The Collecting Taste: Italian Case-Studies between the Nineteenth and Twentieth Centuries,” in European Collections of Scientific Instruments 1550–1750edited by Giorgio Strano Stephen Johnston Mara Miniati Alison Morrison-Low (Leiden: Brill 2009) pp. 191–204: 197.


Tullio Tomba“Poesia e Scienza delle Stelle nel Medioevo Inglese: Un Astrolabio della ‘Tradizione Chaucer’,” FIMAntiquari: Arte viva: Pubblicazione della Federazione italiana mercanti d’arte1994 3 (5): 46–53 p. 49.


In addition to Tomba“Poesia e Scienza” (cit. note 3), see also: Tomba, “Un astrolabio inglese medievale della ‘Tradizione Chaucer’,” Rendiconti dell’Istituto Lombardo sez. B1992 126: 71–82.


Paul Kunitzsch“John of London and His Unknown Arabic Source,” Journal for the History of Astronomy1986 17: 51–57 p. 51. See also Kunitzsch “Star Catalogues and Star Tables in Medieval Oriental and European Astronomy” Indian Journal of History of Science 1986 21 (2): 113–122 p. 120.


John David NorthChaucer’s Universe (Oxford: Clarendon Press1988) pp. 38–86 and in particular p. 38; Eisner (ed.) A Treatise (cit. note 10) p. 105.


Ibid. p. 104.


Ibid. p. 109.


Ibid. pp. 152–153.


Catherine Eagleton“‘Chaucer’s Own Astrolabe’: Text, Image and Object,” Studies in History and Philosophy of Science2007 38: 303–326.


Owen Gingerich“Zoomorphic Astrolabes and the Introduction of Arabic Star Names into Europe,” in From Deferent to Equant: A Volume of Studies in the History of Science in the Ancient and Medieval Near East in Honor of E.S. Kennedyedited by D.A. King G.A. Saliba (New York: The New York Academy of Sciences 1987): 89–104 pp. 92–93; also reprinted with major variants as the chapter “Zoomorphic Astrolabes: Arabic Star Names Enter Europe” in Gingerich The Eye of Heaven: Ptolemy Copernicus Kepler (New York: The American Institute of Physics 1993): 81–101 p. 84.


Walter W. Skeat (ed.)A Treatise on the Astrolabe; Addressed to His Son Lowys by Geoffrey Chaucer A.D. 1391 (London: N. Trübner & Co.1872) pl. II fig. 2; reprinted as: Geoffrey Chaucer A Treatise on the Astrolabe (1391) (Amsterdam: Meridian Publishing Co. 1978) pl. II fig. 2.


Adriano CappelliLexicon abbreviaturarum: Dizionario di abbreviature latine ed italiane (Milan: Hoepli2004) pp. xxiii–xxvi.


Ibid. pp. xxix–xxxi.


Ibid. pp. xxix–xxxi and xxxvi.


Gerald J. Toomer (ed.)Ptolemy’s Almagest (New York: Spinger Verlag1984) p. 387.


Kari Anne Rand SchmidtThe Authorship of the Equatorie of the Planetis (Cambridge: D.S. Brewer1993) pp. 150–185.


Henri MichelTraité de l’astrolabe (Paris: Gauthier-Villars, 1947); reprint: (Paris: Librairie Alain Brieux1976) pp. 142–148; Roland K.E. Torode “A Mathematical System for Identifying the Stars of an Astrolabe and Finding its Age” Astrolabica 1989 5: 53–73 p. 57; Torode “A Study of Astrolabes” Journal of the British Astronomical Association 1992 102 (1): 25–30 pp. 25–26. For critical contributions about such methods see: Emmanuel Poulle “Peut-on dater les astrolabes médiévaux?” Revue d’Histoire des Sciences el Leurs Applications 1956 9: 301–322; Elly Dekker “On Astrolabes and Dates and Dead Ends” Annals of Science 1992 49: 175–184 pp. 177–184.


Milton D. HeifenzPrecession of the Equinoxes Historical Planisphere (Somerville, Massachusetts: Learning Technologies Inc.1997).


Ibid. pp. 316–317.


Ibid. p. 177.


Ibid. p. 198.


Ibid. pp. 206–207.


Ibid. p. 207.


Ibid. pp. 206–207. Eagleton further relates the letters of the hour division of the limb to one method of dividing the compass and the visible horizon citing Chaucer’s reference to “this orisonte departed in 24 partis by this azimutes in signification of the 24 parties of the world” Eagleton “‘Chaucer’s Own Astrolabe’” (cit. note 18) p. 320; Chaucer however is referring to the horizon line on the latitude projection which is indeed divided by the azimuths into 24 intervals of 15 degrees and not to the limb of the mater.


Ibid. pp. 312–314.


  • View in gallery
    Figure 1

    The Tomba-Koelliker astrolabe, front (Museo Galileo: Istituto e Museo di Storia della Scienza, Florence, inv. no. 3931).

  • View in gallery
    Figure 2

    The Tomba-Koelliker astrolabe, back (Museo Galileo: Istituto e Museo di Storia della Scienza, Florence, inv. no. 3931).

  • View in gallery
    Figure 3

    The mater of the Tomba-Koelliker astrolabe, front; detail of the preparation marks for dividing the lost original limb.

  • View in gallery
    Figure 4

    The mater of the Tomba-Koelliker astrolabe, back.

  • View in gallery
    Figure 5

    The rete of the Tomba-Koelliker astrolabe, front.

  • View in gallery
    Figure 6

    Second plate of the Tomba-Koelliker astrolabe, side marked “51:34 london”.

  • View in gallery
    Figure 7

    Astrolabe rete in the Cambridge University Library MS. Dd.3.53, f. 213v (from Gunther, The Astrolabes of the World, 1932, p. 481).

  • View in gallery
    Figure 8

    Astrolabe rete in the Bodleian Library MS. Rawlinson D. 913, fol. 29r (from Gunther, The Astrolabes of the World, 1932, p. 480).

  • View in gallery
    Figure 9

    Detail of the Tomba-Koelliker astrolabe pointer for the star Alhabor (Sirius) shaped as a dog head displaying the so-called “Collar of Esses”.


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