1 For a diagram of a medieval astrolabe, see the Appendix.

2 Cf. ODB s.v. ‘Astrolabe’ and ‘Ptolemy’ and Pingree, D., ‘Gregory Chioniades and Palaeologan astronomy’, DOP 18 (1964) 135-60Google Scholar.

3 For illustrated examples, see Gunther, R. T., The Astrolabes of the World, 2 vols. (Oxford 1932)Google Scholar. For the sole surviving example of a Byzantine astrolabe, see Dalton, O. M., ‘The Byzantine astrolabe at Brescia’, Proceedings of the British Academy 12 (1926) 133-16Google Scholar and the exhibition catalogue L’Art byzantin, art européen 2nd edn. (Athens 1964) no. 549 (pp. 448-9 and 583-4).

4 Discussed by Tihon, A., ‘Traités byzantins sur l’astrolabe’, Physis 32 (1995) 323-57Google Scholar, esp. 325 and 333-40. Hereafter, Tihon, ‘Traités’.

5 Gunther, R. T., Chaucer and Messahalla on the Astrolabe, vol. 5 of Early Science in Oxford (Oxford 1929) vii Google Scholar. Hereafter, Gunther, Chaucer.

6 Tihon, ‘Traités’, 325 and 335-6.

7 (6) ούχ ώς δεομένης τάχα της παρ’ ήμιν διαλεκτικής καί της έντεΰθεν καν το βραχύ συγκροτήσεως, ε’ίπερ οΰδ’ ό μέγας φωσφόρος, ‘iv’ οϋτως ε’ίποιμι, λυχνιαίου χρήζει φωτός, άλλ’ ϊν’ ώνπερ εχοιμεν ίκανώς τούτων καί ύπερεκπερισσοϋ εύποροίημεν ... Manuel Holobolus, Prooemium in translationem Boethii De topicis differentiis. (Text from on-line Thesaurus Linguae Graecae). See Fisher, E. A., ‘Planoudes, Holobolos, and the motivation for translation’, GRBS 43 (2002/3) 77–104, esp. 83-96Google Scholar.

8 Latin text and English translation in Gunther, Chaucer, 137-231.

9 Kunitzsch, P., ‘On the authenticity of the treatise on the composition and use of the astrolabe ascribed to Messahalla,’ The Arabs and the Stars: Texts and Traditions on the Fixed Stars, and their Influence in Medieval Europe (Northampton 1989) item 10, 55-7Google Scholar. Hereafter, Kunitzsch, ‘Authenticity’.

10 Private communication from Ron B. Thomson (5/21/2010) currently undertaking a critical edition of ps.-Messahalla.

11 Latin text from MS. Camb. Univ. Libr., Ii. 3. 3 (dated 1276) in Gunther, Chaucer; Greek version from Oxoniensis Cromwellianus 12 published with introduction, notes and French translation in Une version byzantine du traitê sur l’astrolabe du Pseudo-Messahalla, ed. Tihon, A., Leurquin, R. and Scheuren, C., Corpus des Astronomes Byzantins 10 (Louvain 2001)Google Scholar. Hereafter Tihon et al, Version.

12 Tihon et al., Version, 9-13.

13 See Tihon et al.>, Version, 17; 24-5; 51-2.

14 Gunther, Chaucer, 218.

15 See Tihon et al., Version, 17-8.

16 Chapters 11, 12, 23-31, 33, 38, 39, 41-4; see Tihon et al., Version, 11-3.

17 Fisher, E. A., ‘Planoudes’ technique and competence as a translator of Ovid’s Metamorphoses’, BS 62 (2004) 143-60Google Scholar.

18 Gunther, Chaucer, vi.

19 See Kunitzsch, P., Observations on the Arabic reception of the astrolabe’, in The Arabs and the Stars: texts and traditions on the fixed stars, and their influence in medieval Europe (Northampton 1989) item 7, 248 and 245Google Scholar.

20 This vocabulary is cited in Tihon et al., Version, 17-8.

21 For examples of such 12th-century Greek calques in translations of the Byzantine chancery, see Gastgeber, C., ‘Die lateinische Übersetzungsabteilung der byzantinischen Kaiserkanzlei unter den Komnenen und Angeloi’, in Balard, M., Malamut, E., Speiser, J.-M. (eds.), Byzance et le monde extérieur (Paris 2005) 107-8Google Scholar. For examples in a translation of Planoudes, see Fisher, E., ‘Planoudes’ De trinitate, the art of translation, and the beholder’s share’, in Papanikolaou, A. and Demacopoulos, G. (eds.), Orthodox Readings of Augustine (Crestwood NY 2008) 41–61, esp. 51-3Google Scholar.

22 Kunitzsch, ‘Authenticity’, 250, no. 7.

23 Tihon, ‘Traités’, 325, 335.

24 Delatte, A., Anecdota atheniensia et alia, vol. 2 (Liège 1939) 254-62Google Scholar. Hereafter, Delatte, Anecdota.

25 Segonds, A.-Ph., Jean Philopon, traité de l’astrolabe (Paris 1981) 83-4Google Scholar. Hereafter, Segonds, Philopon.

26 Segonds, Philopon, 84; examples in Delatte Anecdota, 259 lines 5, 10, 19 etc. See Morrison, J. E., The Astrolabe (Rehobeth Beach DE 2007) 9 Google Scholar. Hereafter, Morrison, Astrolabe.

27 Tihon discusses this text in ‘Traités’, 335-6.

28 Delatte, Anecdota, 261 line 19.

29 Delatte, Anecdota, 254 lines 6-8.

30 For these Arab astronomers, see Kunitzsch, ‘Authenticity’, 42-3 and 50-1.

31 Delatte, Anecdota, 254 lines 1-9.

32 Segonds, Philopon, 84.

33 Pingree, D., The astronomical works of Gregory Chioniades. Vol. I: The Zij al-‘Ala’ I, Part I Text, translation, commentary (Amsterdam 1985) 18-9Google Scholar (hereafter, Pingree, Astronomical works) and ODB s.v. ‘Chioniades, Gregory’.

34 Duhoux-Tihon, A., ‘Les tables astronomiques Persanes à Constantinople dans la première moitié du XVIe siècle’, B 57 (1987) 475 n. 31 Google Scholar. Hereafter, Duhoux-Tihon, ‘Tables’.

35 For Chioniades’ career, see Westerink, L. G., ‘La profession de foi de Grégoire Chioniadès’, REB 38 (1980) 233-15CrossRefGoogle Scholar (hereafter, Westerink, ‘Profession’), and more recently Bydén, Börje, Theodore Metochites’ Stoicheiosis Astronomike and the study of natural philosophy and mathematics in Early Palaeologan Byzantium (Gothoburg 2003) 242-8 (hereafter, Bydén, Metochites)Google Scholar.

36 Pingree, Astronomical works, 36 line 5.

37 R. Mercier, “Shams al-Din al-Bukhari,” accessed 6/4/12 at http://islamsci.mcgill.ca/RASI/BEA/Shams_al_Din_al-Bukhari_BEA.htm

38 Westerink, ‘Profession’, 239.

39 Tihon, ‘Traités’, 333.

40 Segonds, Philopon, 80-2.

41 Delatte, Anecdota, 263-71.

42 Equation τατίλ = ta’díl; altitude ήρτιφά or ίρτιφάχ = irtifa’; ascension ματαλέ = matâli’; equator μαντουλι-ναάρ = mu’addil-i nahát, Tihon, ‘Traités’, 334-5, citing an unpublished study by Anne-Marie Doyen.

43 Delatte, Anecdota, 263 lines 2-6.

44 Tihon, ‘Traités’, 333-t.

45 My colleague Mohssen Esseesy in a private communication (10/10/2009).

46 Tihon, ‘Traités’; 333, Segonds, Philopon, 102 n. 55.

47 Text transcribed from Cod. Marc. Gr. 390 f. 154.1 have replicated as far as possible the punctuation of the manuscript; see Noret, J., ‘Notes de ponctuation et d’ accentuation byzantines’, B 65 (1995) 69–88 Google Scholar.

48 I thank Dr. Anne-Marie Doyen for generously allowing me to consult her unpublished edition and annotated French translation of this text (Le trait sur l’Astrolabe de Stamps le Persan, Université Catholique de Louvain, 1978-9); also Alice-Mary Talbot, Stratis Papaioannou and Denis Sullivan for perceptive comments on translation and Rob Farber and other members of Denis Sullivan’s Greek Reading Group (Ted Perlman, Hardee Mahoney and Sandy Sondarajan) for illuminating discussions.

49 Philoponus, Cf. Joannes, In Aristotelis libros de anima Commentaria, ed. Haydruck, M., Commentaria in Aristotelem Graeca 15, 75. 11-1 (Berlin 1897 Google Scholar): κοά ή στάσις δέ έπί πάντων θεωρεΐτοα- κοά γάρ καί τά άεικίνητα στάσεως μετέχει, οϋ μόνον τφ τήν όλότητα έστάναι, άλλά κοά αύτο το μένειν έπί της άεικινησίας στάσις έστί. See also Suidae lexicon ed. Adler, A., 1 (Leipzig 1928-38) 4093.29Google Scholar, and Michaelis Pselli philosophica minora, ed. O’Meara, D. J., 2 (Leipzig 1989) 39.2 Google Scholar.

50 The astrolabe that accompanied Siamps’ treatise was evidently crafted of precious metal; ‘silvery zone’ seemingly refers to the offset circle on the rete or aranea of the instrument, which may have been of silver, and ‘the circumference <of the sun’s journey>’ may designate the edge of the plate (reading the ms. περιφορά as a variant of περιφερεία). Astrolabes constructed for use in the northern hemisphere show a projection of the celestial sphere only as far as the Tropic of Capricorn. ‘This range’, observes Morrison, ‘includes the sun’s annual motion and represents almost all of the sky visible from northern temperate latitudes’ (Morrison, Astrolabe, 6-7 and diagram p. 10).

51 The round plate of this instrument was apparently of silver and thus resembled the moon.

52 Ptolemy designated seven ‘classic’ climate zones or κράσεις, latitudes where the length of the year’s longest day varied by one-half hour. An astrolabe that included a plate for each of these seven zones encompassed the known world and was a ‘universal’ astrolabe (see Morrison, Astrolabe, 58-9).

53 The moon has four phases, while the back of the astrolabe shows four quadrants marked by the north-south and east-west diameter of the mater (cf. Morrison, Astrolabe, 15).

54 I offer a tentative translation of this sentence, which is cryptic and perhaps corrupt in Greek. ‘Twenty-eight stations’ refers to the Lunar Mansions, a very ancient division of the ecliptic marked on all Islamic instruments to represent the movement of the moon relative to the stars through a sidereal month of 28 days and associated with calculations significant for astrology (cf. Morrison Astrolabe, 143). The ‘seven zones’ may refer to the divisions sometimes marked on the side of the shadow square of Islamic instruments (cf. Morrison, Astrolabe, 115) or to the latitudes of the seven climate zones. For the occurrence and various forms of lunar mansions on Islamic/Arabic astrolabes, see Ackermann, S., ‘The path of the moon engraved. Lunar mansions on European and Islamic scientific instruments’, Micrologus 12 (2004) 135-64Google Scholar. I am indebted to an anonymous referee for this reference.

55 The wise are described as ‘stars of heaven’ in Daniel 12, 3: mi oí συνιέντες φανοΰσιν ώς φωστηρες τοΰ ούρανοΰ καί οί κατισχύοντες τοΰς λόγους μου ώσεί τά αστρα τοϋ ούρανοΰ εϊς τον αίώνα τοΰ αίώνος. ‘And the wise shall shine as the brightness of the firmament, and some of the many righteous as the stars for ever and ever’ (tr. Brenton).

56 The structure of this passage is confusing and possibly corrupt; it yields only a general sense of the author’s meaning, that the Creator uses the stars and the prophets to reveal his guidance to humanity.

57 For the Greek text with a French translation of this paragraph from έπηλθέ μοι (line 19 ‘This desire came to me...’) to ή xòv άστρολάβον (line 25 ‘... than the astrolabe’) see Duhoux-Tihon ‘Tables’, 475-6 n. 31.

58 Mohssen Esseesy commented in a private communication (10/10/2009) that the spelling ‘Siamps’ (Σιάμψ), or ‘Samps’ (Σάμψ) in Chioniades’ text, may represent a dialect variation of the Arabic ‘Shams’ or ‘Sams’ (‘Sun’). Tihon considers the spelling variation to be the result of different milieus in which the name was transliterated (Tihon, ‘Traités’, 334). It is interesting that ‘Siamps’/‘Samps’ does not reveal his full name, ‘Shams al-Din al-Bukhari’ (‘Light of the Faith from Bukhara’).

59 The author’s reasoning is obscure and the text may be corrupt; Siamps/Shams seems to contend that he requires a more powerful patron in order to complete his own identity, just as the moon requires the light of the sun in order to shine.

60 The author’s logic seems to be that he has the name ‘Sun’ but possesses no light characteristic of the sun except that reflected from the true sun or emperor; thus the author is like the moon.

61 άστρόλαβος is literally ‘star-taker’ in Greek. I follow Doyen in understanding the otherwise unattested word ίωνα to refer to the Greek language (‘yunani’ in Persian, from ‘Ionian’; I thank my colleague Muriel Atkin for this information).

62 Arabic authors of astrolabe treatises in the 12th and 13th centuries frequently cite this bizarre metaphor, which entered the Arabic tradition due to a faulty Greek etymology presented in earlier texts. The 10th-century encyclopedist al-Khwarizmi derived asturlab from Greek as mir’at al-shams, ‘mirror (= λαβ−) of the sun’, apparently referring to the circular, flat shape of an astrolabe, while the Persian astronomer Kushyar (fl. ca. 1000) explained asturlab as mizan al-shams, ‘balance (= λαβ−) of the sun’, perhaps relying upon a misreading of al-Khwarizmi’s mir’ at. Arabic authors continued to describe the astrolabe as the ‘balance of the sun’ into the 18 century. See King, D. A., ‘The origin of the astrolabe according to the medieval Islamic sources’, Islamic astronomical instruments (London 1987 Google Scholar) item III. Of the numerous Arabic derivations of asturlab cited by King, Siamps may favor the metaphor ‘balance of the sun’ because the astrolabe represents both the position of the moon (= Siamps) and of the sun (= Andronikos II).

63 i.e., the astrolabe.

64 Again, an extended metaphor unclear in its reference but perhaps meaning that the emperor will balance or assess Siamps’ helpful role in presenting him with an astrolabe and instructions for using it, thus enabling the emperor to assess relationships in the heavens.

65 An anonymous referee notes as a parallel two treatises on the use of the astrolabe dedicated to European rulers, that of Adelard of Bath dedicated to Henry II (England, mid 12th century) and that of Pelerin de Prusse to Charles V (France, mid 14th century). See North, J. D., ‘Some Norman horoscopes’, in Burnett, C. (ed.), Adelard of Bath: an English scientist and Arabist of the early twelfth century (London 1987) 147-62Google Scholar, esp. 159, and Laird, E. and Fischer, R., Pèlerin de Prusse on the Astrolabe: text and translation of his Practique de Astralabe (Binghamton, NY 1995) 1–8 Google Scholar.

66 Tihon, ‘Traités’, 334.

67 Duhoux-Tihon, ‘Tables’, 476; Mavroudi, M., ‘Exchanges with Arabic writers during the late Byzantine period,’ in Brooks, S. T. (ed.), Byzantium: faith and power (1261-1557), (New Haven 2006) 65 Google Scholar. Hereafter, Mavroudi, ‘Exchanges’.

68 See Aga-Oglu, M.,‘Two astrolabes of the late Safawid period’, Bulletin of the Museum of Pine Arts 45 (1947) 79–84, esp. 80Google Scholar.

69 ... δόξαν ειναι τινα παλαιάν έπικρατήσασαν παρ’ αύτοΐς, ώς φθαρήσεσθαι τήν έκείνων βασιλείαν ύπό ‘Ρωμαίων τη τέχνη της άστρονομίας χρωμένων, παρ’ έκείνων πρότερον ταύτης λαβόντες ... Chrysokokkes, 357. 14-17. See also Westerink ‘Profession’, 236 and Mavroudi, ‘Exchanges’ 65 and 71 n. 5.

70 For a possibly parallel situation in the Islamic world of the late 13 century, see Ward, R., ‘The inscription on the astrolabe by ‘Abd al-Karim in the British Museum’, Muqarnas 21: Essays in honor of J.M. Rogers , eds. Behrens-Abousief, D., Contadini, A., (Leiden 2004) 345-57, esp. 354Google Scholar.

71 Mavroudi ‘Exchanges’, 63.

72 See Fisher, E., ‘Manuel Holobolos, Alfred of Sareshal, and the Greek translator of ps.-Aristotle’s De plantis ’, Classica et Mediaevalia 57 (2006) 189–211, esp. 199Google Scholar.

73 Bydén, Metochites, 240-1; see also Tihon, A., ‘Astrological promenade in Byzantium in the early Palaio-logan period’, in Magdalino, P. and Mavroudi, M. (eds.), The occult sciences in Byzantium (Geneva 2006) 267-90, esp. 273-80Google Scholar.

74 Pingree, ODB s.v. ‘Astrolabe’ and Morrison Astrolabe, 58.

75 Morrison, Astrolabe, 1.

76 For the principles governing the operations of the astrolabe, its history and the parts composing it, see Morrison Astrolabe and his website, http://www.astrolabes.org. I thank Morrison for his expert and patient advice on technical matters in this paper.

77 A western astrolabe had also a rule (ostensor) that rotated over the rete.