Ghazan Khan's astronomical innovations at Maragha observatory.

• Author: Mozaffari, Mohammad S
• Position: Essay

1. INTRODUCTION

   Everything we know about the observatory in Tabriz founded by Ghazan Khan (r. 12711304), the seventh ruler of the Ilkhanid dynasty of Persia (1295-1304), was published by Aydin Sayili some fifty years ago). (1) Relying on primary historical sources, he presented an adequate description of its astronomical activities and of the many skills of Ghazan Khan in the field of observational instrumentation. (2) Sayi1i also presented a good overview of the Maragha observatory from 1260-1283, (3) but due to a lack of reliable evidence for the period after ca. 1280, he made some statements--especially concerning Ghazan Khan's astronomical innovations--that could not be substantiated. A recently discovered treatise has now revealed the exact type and location of Ghazan Khan's innovations, which we enumerate below. Our treatise begins where Sayili left off and appears to give dependable information that we can use to illuminate the later period at the Maragha observatory, during which very little is known concerning the type and extent of astronomical activity.

   We begin by introducing Rashid al-Din Tabib's claim as to Ghazan Khan's astronomical activities and innovations. We then examine the validity of the claim with the help of the newly discovered treatise, as well as verify the reliability of the information in the treatise as to the type, structure, and location of Ghazan Khan's newly made instruments. For this purpose, it was necessary to examine Ghazan Khan's innovations both in the context of the Maragha astronomical tradition (as the dominant tradition of the time) and in the context of medieval observational instrumentation in general. We follow with a general classification of the instruments and argue their possible relation to later Western models; and we conclude by describing the instruments in the order in which they appear in the treatise.

2. HISTORICAL BACKGROUND

   According to his vizier, Rashid al-Din Tabib (d. 718/1318), Ghazan Khan was a prominent artisan, an alchemist, an expert in medicine and botany (he invented a new antitoxin called tiryaq-i ghazani), and a mineralogist, as well as being interested in theology. (4) In his youth he was taught by Mongol Buddhist monks, but he later converted to Islam. (5) Upon his victory over the Mamluk army at the battle of Wadi 1-Khaznadar, Ghazan arrived in Maragha, the site of the renowned observatory built in the thirteenth century under the direction of Nasir al-Din al-Tusi, where he resided from 15 Ramadan until 24 Shawwal 699 (June 4--July 13, 1300). (6) After he arrived,

   On the next day, he went to watch the observations; he looked at all the operations (a'mal) and instruments, studied them, and asked about their procedures, which he understood in spite of their difficulty. He ordered the construction of an observatory next to his tomb in Abwab al-Birr tin the district] of al-Sham in Tabriz (7) for several operations. He clearly explained how to do those operations so that local wise men marveled at his intelligence, because such work ('amal) had not been done in any era. Those wise men said that constructing it [the observatory] would be extremely difficult. He guided them, whereupon they commenced building it and they finished it per his instructions. Those wise men and all the engineers agreed that nobody had done such a thing before nor had imagined doing it. (8) Thereafter,

   On several occasions he went to Maragha, asked for an explanation of the instruments there, examined their configuration (kayfiyya) carefully, and studied them. He had a general idea of them. As per his nature (tab'), everything having to do with the siting and the building of the [Maraghal observatory he commanded to construct. (9) Rashid al-Din Tabib also reported that he ordered the construction of a hemispherical instrument (gunbad) for solar observations at Tabriz observatory and described it in technical detail for his astronomers. (10)

   The Maragha observatory

   The Maragha observatory was built in 1259 by Hulegu (d. 1265), the founder of the Ilkhanid dynasty; for the circa fifty-eight years it functioned, it represented the acme of Islamic astronomy. We have divided the astronomical activities in Maragha into two distinct periods: the first from its beginnings to 1283, the second from ca. 682/1283 to 716/1317. (11) Even before the construction of the observatory it appears that observations had been undertaken in Maragha: in his treatise on the astrolabe (Fi kayfiyyat al-tastih al-basit al-kuri), Ibn al-Salah al-Hamadhani (d. 1153) wrote that in MarAgha he found the magnitude of 23;35[degrees] for the obliquity of the ecliptic (mayl al-kulli); (12) there also appeared three important zijes (astronomical handbooks or tables) that later had bearing on work undertaken during the second period: al-Khazini's Zij al-sanjari (510/1116), (13) al-Fahhad's Zij of ca. 1166, (14) and Zij al-shahi of Husam al-Din al-Salar, who was killed by order of Hulegu on 8 Muharram 661/November 22, 1262. (15) The first two were translated into Greek while the third was mentioned in these translated texts. (16)

   During the first period of the observatory, two prominent zijes were written: al-Tusi's Zij-i ilkhani in Persian and Muhyi 1-Din al-Maghribi's Adwar al-anwar in Arabic (completed in 1275). (17) Both were reliably quoted in the second period, by works either connected to the observatory, such as al-Wabkanawi's Zij-i muhaqqaq-i sultani (18) and Greek translations made by Gregory Chioniades, (19) or independent of it, such as al-Kamali's Zij-i ashrafi, completed by the end of the Persian year 681 (i.e., March 12, 1303) in Shiraz. (20) The instrument-maker in the first period was Mu'ayyad al-Din al-'Urdi (d. 1266) (see below).

   In the second period there were at least five outstanding scientists in the field of mathematical science connected with Ghazal Khan's court:(21)

   1. Qutb al-Din al-Shirazi, who apparently spent his time in a solitary manner between 1283 and 1311 in Tabriz. He revised his Zij-i ridwani in 690/1291-2. (22)

   2. Shams al-Din Muhammad al-Wabkanawi al-Bukhari, the author of Zij-i muhaqqaq-i sultani. (23) In this work we are confronted with one of the most preeminent Islamic zijes produced from direct observations. He sharply criticized al-Tusi's Zij-i ilkhani for the reason that the calculated positions of the seven planets were never in agreement with actual observations, and because it was only a copy of earlier zijes, especially in the fundamental planetary parameters. He referred to Muhyi 1-Din al-Maghribi's Adwar as being "based on the new Ilkhanid observations" (i.e., Muhyi 1-Din's own observations) for the sake of making a distinction between it and Zij-i ilkhani, which was assumed to be obtained through the "Ilkhanid observations" (i.e., the observational plans supervised by al-Tusi and performed by his colleagues). (24)

      Al-Wabkanawi introduced some new topics such as a rule for conjunctions between Jupiter and Saturn, the report of their triple conjunction in 1305-6 and their single one of January 1286, and the exact report of the annular eclipse of January 30, 1283 in detailed numerical values. (25) The period of his observations, as he himself says, extended over forty years. (26)

   3. Shams al-Din Muhammad b. Mubarakshah Mirak al-Bukhari al-Hirawi (d. 1340).

   4. Nizam al-Din al-Nisaburi, who is wrongly known as the author of Zij al-'ala'i, actually written by al-Fahhad.

   5. Shams al-'Ubaydi, a mathematician. (27)

      Also during this period Gregory Chioniades (d. ca. 1320) was in Tabriz where he translated al-Khazini's Zij al-sanjari, al-Fahhad's Zij al-'ala'i, and a text on 'dm al-hay'a (28) into Greek. (29) According to Chioniades, he used the oral instructions of a person named [SIGMA][alpha][mu][psi][PI]ov[chi]a[rho][eta][zeta] born at Bukhara on June 11, 1254, (30) who is most likely Shams al-Din Muhammad al-Wabkanawl. al-Bukhari. (31) In his As'ila wa-ajwiba ("Questions and Answers"), Rashid Tabib answered the theological questions of a "Frankish sage" (hakim-i farang), (32) who is probably the same Chioniades. (33)

3. THE TREATISE

   The anonymous Persian treatise studied in this article is entitled Risalat al-ghazaniyya fi l-alat al-rasadiyya ("Ghazan's Treatise on Observational Instruments") and provides entirely new information about Ghazan's approach to observational instruments and his innovations in this field. We find a full description of twelve instruments allegedly invented by him, which were employed at the observatory at Maragha instead of at his "new" observatory in Tabriz (our author clearly says this, and he also has included tables of oblique ascensions for the latitude of Maragha).

   Three copies of this treatise are preserved in libraries in Tehran (34) --in Sipahsalar Library (no. 555D, fols. 15v-49v, henceforth S), in the library of the Parliament (no. 791, pp. 29-97; henceforth P), and--an incomplete one--in Malik National Library (no. 3536, pp. 41-56; henceforth M). (35) The manuscript collections of which S and P are a part are similar in many aspects; they appear to have been copied by a single scribe, with the title ra'is al-kuttab, on Thursday, 23 Jumada 11 1294 (July 5, 1877). (36)

   After praising God and introductory words on the necessity of astronomical instrumentation, the treatise begins with the description of the five instruments mentioned in Ptolemy's Almagest: halqa nuhasiyya (two meridian rings, I, 12); lubna (quadrant, I, 12); another halqa nuhasiyya (equinoctial ring, III, 1); dhat al-halaq (armillary sphere, V. 1); and dhat al-shu'batayn (parallactic instrument, V. 12).

   The description of no. 3 makes clear that it has been wrongly given the name of no. 1 in the list (in all ms copies); it should be correctly named halqat Although both instruments were mostly made of copper (nuhas), only the instrument known as "two meridian rings" was customarily called halqa nuhasiyya. (37)

   The author of the treatise reviews the...