The surface of a fluid in a container rotating around vertical axis at a constant angular speed gets form of the rotating parabola. The mirrors having such form are ideal for the telescopes. This well known physical phenomenon was used in 1908 by noted physicists Robert Wood in his mercury telescope. This most "useless" his invention gained large popularity for him. His telescope, which was a rotating dish with mercury fixed at bottom of a well under cowshed, became sensation. Standing on edge of the well, people looked downwards and were amazed by image of stars, which were like bright electrical lamps hanging in the air.
"New telescope will discover a mystery of the Universe. Is Mars inhabited?"
"Mercury telescope, invented by genius from Baltimore, brings Moon near to Earth up to several miles" - such headings filled in pages of leading newspapers. "Associated Press" and popular scientific syndicates also snatched at new invention and the cowshed became a "place of pilgrimage" for scientists and curious people.
These quotations were taken from the book by Seabrook, W. "Doctor Wood, Modern Wizard of the Laboratory."  [1]
In the beginning of XV century Abd ar-Rashid al-Bakuvi (native of Baku) in his book "On monuments and miracles of powerful king" (reduced version) [2] described an event of six hundred years old, which took place in town Nahshab (near Buhara ), in strong degree reminding Baltimore phenomenon.

"(110) Nahshab is a known town in Horasan. There are many holies and sages there. This is a place of descend of sage Ibn al-Mukaffa, who dug a well, from which the moon appeared. People saw it and it looked like true moon. This has become known everywhere and people gathered in Nahshab to see the moon and marvel at it. Ignorant people considered him a wizard, but it was nothing but engineering trick and reflection of moon beams: a big basin full of mercury was found at bottom of the well. This has resulted in a surprising miracle spoken about everywhere, and which became so famous that people mentioned it in verses and sayings…"

No comments can be added here. It's an obvious fact of successful scientific discovery, consisting in strong evidence of telescopic observations held in 70-80th years of 8th century by Mukanna (why Mukanna and not Mukaffa see below). Considering specifics of historiography sources, which is complicated in this case by time remoteness of first primary source (XV century) and the described event (VIII century), as well as unknown scientific subject (telescopic observation of moon), this information of Bakuvi can be regarded as quite reliable and authentic.
One can consider justifiable Bakuvi's mistake of engineering merits of Mukanna's device. He believed that in Mukanna's device there had been a simple regular reflection from surface of mercury. Bakuvi missed the fact that with such simple way it was impossible to surprise numerous crowd of the people.  He couldn't understand that image similar to true and big moon can only be given by concave surface of mirror, i.e. mercury telescope. Such surfaces give bright and enlarged images, which can only be seen by unaided eye from a certain point. People, who knew nothing about such mirrors, came up at night time to well dug at bottom of Siam, looked downwards and saw bright and big moon. And they trusted that shining in the sky true moon came out from Mukanna's well.
Mukanna headed anti feudal and anti Arabian revolt, in Central Asia 70-80-th years of 8 century, known as well as movement" of the people in white clothes ".Just around 781 A.D. after the death of Mukanna, the revolt was pressed down. However till the 12-th century there have been his followers.

MOKANNA (al-Moqanna', the Veiled), the name given to Hakim, or 'Ata, a man of unknown parentage, originally a fuller in Merv, who posed as an incarnation of Deity, and headed a revolt in Khorasan against the caliph Mandi. For about three years he sustained himself in the field against the troops of the caliph and for two years longer in his fortress of Sanam; then, reduced to straits in 779, he and his followers took poison and set fire to the fortress. Much is related to his magical arts, especially of a moonlike light visible for an enormous distance which he made to rise from a well near Nakhshab. He is the hero of the first part of Moore's Lalla Rookh.

Along with manuscript of Bakuvi, there are numerous historical sources and legends about personality and activities of Mukanna, about his "false" moon, "moon of Nahshab", "moon of Siam", which became metaphor for poets. He was also called, in the Persian tongue, Sazindah-mah, or the moon maker.
The arabian historian Ibn Khallikan (1211-1282) at his " Biographical Dictionary» write:
AL-MUKANNA AL-KHORASANI. Al-Mukanna al-Khorasani (the veiled impostor of Khorasan), whose real name was Ata, but whose father's name is unknown to me, began his life as a fuller at Marv (town in Uzbekistan-author)). Having acquired some knowledge of (natural) magic and incantations, he pretended to be animated by the divinity, which had passed to him by transmigration, and he said to his partisans and followers: "Almighty God " entered into the figure of Adam, and it was for that reason that he told the " angels to adore Adam, and they adored him except Iblts, who proudly refused (1), " and who thus justly merited the divine wrath. From the figure of Adam, " God passed into that of Noah, and from Noah to each of the prophets successively, and of the sages, till he appeared in the figure of Abu Muslim al- " Khorasani (vol. II. p. 100), from whom he passed into me." His assertions having obtained belief with some people, they adored him and took up arms in his defence...he never let his face be seen, but always veiled it with a mask of gold, and it was from this circumstance that he received his name. The influence which he exercised over the minds of his followers was acquired by the delusive miracles which he wrought in their sight by means of magic and incantations. One of the deceptions which he exhibited to them was the image of a moon, which rose so as to be visible to the distance of a two months' journey, after which it set ; and he thus inspired them with the firmest belief in his words. It is to this moon that Abu '1-Ala al-Maarri (vol. I. p. 94) alludes in the following line :
"Awake (from the delusions of love) ! that full moon (2) whose head is shrouded in a veil is a false and delusive object, like the moon of the veiled impostor. This verse forms part of a long kasida. Abu '1-Kasim Hibat Allah Ibn Sina al-Mulk, another poet whose life we shall give in this work, speaks of this moon also in a long poem of his, where he says : Beware! the veiled (impostor's) rising moon is not more pregnant with magic than the glances of that turbaned moon... "

At Nezami's poem "Khosrov and Shirin" is three times addresses to the Nahshab moon metaphor:
"But she is not a moon, she is a mirror and a mercury.
Her figure as of Nahshab moon... "
"Who has grasped a throne yours? You see he is only Mukanna,
He create a moon for the real  deceit.
But with  this moon the world nevertheless will be mist:
 The round sheet of iron not lighten its "

The Hungarian historian Arminius Vambery ("About Mukanna")  : "Moon of  Nahshab - Giving out itself for the prophet Hashim ibn- Hakim Mukanna at the request of followers in Nahshab has pulled out from well a brilliant subject similar to the moon. From here expression " the moon of Nahshab" has become a favorite metaphor of the persian language  poets.

Ella C. Sykes after two visits in Persia in the beginning of the 20-th century wrote [3]: "Every legend about Al Mukanna speaks of the mask, or veil, which he habitually wore to conceal a countenance of surpassing ugliness; but the reason he himself gave was that he covered his face in order not to dazzle his disciples with its effulgence. There is also the tradition that he caused a "false moon" to rise from a certain well, which was visited night after night by crowds of people anxious to see this remarkable phenomenon. It gained for him hundreds of converts, and the "Moon of Al Mukanna" is mentioned in two Persian poems, such an impression did the Veiled Prophet and his dramatic death make on his own and succeeding generations."

However, the Europeans had an knowledge about optical artifice of Mukanna much earlier. In 1697 in Paris was issued the famous book of the French orientalist Bartholomew d'Herbelot "Bibliotheque orientale ou Diction-naire uaiversel, contenant tout ce qui fait connaitre des peuples d'Orient" [4]. The orient library of d'Herbelot based on the information's of the Arabian historians hostile to Mukanna and his movement. The English poet Thomas Moor too has appeared in captivity of the prejudiced and unfair relation to the person of Mukanna. Included in own poem "Lalla Rook" a part devoted to Mukanna - "The veiled prophet of Khorasan" he named Mukanna as a veiled spirit of Evil.

In modern prose the veiled prophet has returned with the story of Jorge Luis Borges "Hakim, the Masked Dyer of Merv".

Mukanna also is the author of the second optical artifice, which also has the direct relation to telescopes. Muhammad Narshahi (989-th years) informs of Mukanna that "he was by origin from outskirts of Merv, from village, which is called Kaza; his name was Hashim, son of Hakim. He was first engaged in wash-house, and then devoted himself to science and gathered knowledge of various kind… He read many books on ancient sciences and gained much skill in astrology… He got the name of Mukanna because he walked with clothed head and face… 50 000 people of Mukanna's army, of citizens of Mavarannagr, of turks and others, gathered to the gates of Mukanna's fortress and with kowtow asked him to favour them with his contemplation… He ordered each woman, which were in his fortress in amount of 100…, to take mirror, go up on top of the fortress and hold each mirror against other. When sun beams fell on earth and all women took in hands their mirrors and held them equally, people had already gathered together; when sun illuminated mirrors the light flooded all over the outskirt because of their reflection. Then Mukanna told his slave: "Tell my slaves that God will show them his face - let them look." They looked and saw that all the world was apparently flooded with light; they got frightened and kissed the ground at once…"

This quotations apart from biographic information, demonstrates as well his profound knowledge in catoptrics (reflection of light). Unlike Archimedes, Mukanna by way of using mirrors in pairs achieved maximum possible illumination by sun light. He actually for the first time used coelostatic (in this case heliostat) optical system, widely used in modern solar telescopes. He apparently used such optical system also earlier, over Nahshab well at foot of Siam, for expansion of visual field of his vertical mercury telescope.
In the opposite case he could only arrange approximately 0.5-1 hour moon shows during some night. Along with that it should be noted that observations of moon at Nahshab latitude (around 40 degree) could only be possible during several days when at the time of upper culmination the moon could illuminate by inclined beams the bottom of wide and non deeper well.

Historic sources witness that his show continued during all the time that moon shone in the night sky:
"…Mukanna Mervezi built in Mavarannagr some device; he brought something like moon out of a mountain at the same time as moon rose so that people of that region saw; he used that trick for a long time. When he turned people away from Islam and shariat, he declared himself God" - writes Nezami al-Mulk on his famous book "Siasetname".

 

Fig.1. Optical scheme of the suitable ancient variants for the mercury telescope. 1, 2 -rotating
and stationary basin with mercury, 3- iron mirror

In medieval east the Mukanna's optical experiments   were so popular that almost all unknown  optical phenomena considered as his miracles. In the known composition (compilation) "Adjaib ad-Dunya" ("The Miracles of the World ") are a mention of one such phenomenon probably working to this day:   
" In limits of Syria there is a huge mountain. During the reaping barley on that mountain there is bright light and again about the next year disappears. Speak, that a miracle it has created Mukanna. Bu 'Ali Hazen was directed here to look, that it for [light] and as him have made. And here Хазин has left here, has experienced difficulties, has seen the light, but to understand true not could . He has told: " Can, on the mountain solar light falls, and under a mountain there is a water, which reflects it similarly to the moon ".  

Bu 'Ali Hazen is the Arabian scientist Ibn al-Haytam (965-1038), known in Europe as Alhazen, the author of the first large work on an optical theme describing as optics of a human eye forms the image on a retina. He are considered "as the father of optics", as man who has offered worthy alternative of the Greek theory. In the composition "About to light a mirror on conic sections" Alhazen mentions experiments of ancient: the mirrors having the form of  rotating parabola, collect all beams in one point and make stronger action, than other mirrors.

In particular, he for the first time has given a scientific explanation to the phenomenon of twilight, that also is argument for the benefit of an identification him with Bu 'Ali Hazen. The historians for Bu 'Ali Hazen from "Miracles" give out the Persian historian and collector of jokes Abu 'Ali Ahmad  bin Muhammad Miskawayh al- hazee, recognizing that treasurer, as which he served within 5 years, on - Arabian tongue, as " al-ha- zin ".
Hardly he could undertake such far travel from Baghdad in Jerusalem and there from further away, in mountains and to give (though also erroneous) a physical explanation to the atmospheric optical phenomenon. And Ibn al-Haytam could for the unknown optical phenomenon go on such far.
The truth, can still apply for a name Bu 'Ali Hazen another scientific, Turkmen al-Hazene. Therefore, this question requires the further specification.

Fig.2. Mukanna's ray above mountain Kartdag of Great Caucasus	Fig.3. Ibn al Haytam (Alhazen)

 

Repeating each summer (can be, and to this day) above this mountain (now this mountain has the name Khirbat el-Mukanna) optical phenomenon is the twilight rays--anti crepuscular rays frequently noticed in different lands of world (fig.1). They occur as a result of closing of coming light of the  Sun by separate clouds or mountain tops which are taking place behind horizon.           
On Tibet of these rays name " as rays of Buddha ". In the syrian mountains name " as Mukanna's rays ".    
In middle of the"Miracles of World" is the story about the other event, as occured on Herbat el-Mukanna. Here given district already has the name, worthy name of the  book: "the mountain, where Муканна has stolen the Moon". In this case Муканна of the obvious form is suspected in the device there by some wizard crevices, from which it is impossible to pull out a hand. The name of a mountain - place of "theft" of the Moon, presence a crevices and light beam above a mountain allows completely to restore a full picture of the legend:
Mukanna through wizard crevices has stolen the local Moon. The trace left by the Moon, as a light beam testifies to it. Here, he whence took the moon, which in Nahshab lifted from well.
"Ostensibly this moon, which covered up to distances three parsek, during sixty of night shined in the sky and at this time in the sky two moon were observed. The people from all light were confused with this of mah--i (moon, on persian) musanna (false, on arabian). This moon named as mah-i Siam, mah-i Mukanna, mah-i Kesh, mah-i Nahshab" - so describes its explanatory dictionary of turkish language "Kamusi Osmani".    


It is considered devices of telescopes with a liquid mirror, including mercury mirror, to this day rather inexpensive and easy. It is quite possible, that the ancient astronomers knew about it. However, the greatest chance nevertheless was of Mukanna. Being engaged in youth the laundries by craft, do not know how many time he noticed unusual optical property of a surface turning waters. Another would not become to pay attention to everyone's there not clear phenomena. But, not Mukanna.

The above-stated attempt of Alhazen to explain "Mukanna's beams" by simple mirror reflection shows, that in Х-ХI age such explanation could take place and for the " moon of Nahshab ". However,  it was possible "to win" Mukanna by used the  his  weapon, by recurrence of his "tricks".  Reach up to now correspondence - discussion of Abu Reyhan Beruni with the Ibn Sina shows, that despite of all diligence of Beruni, as was unshakable  position of the erroneous theory of Aristotle. The Aristotle  theory of light reducing all optical phenomenon to reflection of light , be it a refraction in a lens or in water, even the radiation of the Sun; treating of vision, as beam emission of an eye, and light, as "soul" of environment. Probably for this reason Alhazen could not publish the works and was compelled to emigrate to Europe. Excessive employment by the speculative philosophy of antiquity has developed in large barrier between a science and practice. The optical experiments of Mukanna have remained unsurpassed, even not clear for the following generations.
That fact, that Ibn al - Mukaffa in the book of al-Bakuvi is named as the owner  of the " Nahshab well ", probably, there is a result of a spelling  mistake. The Arabian letters "n" and "f" have the close figure . Ibn al-Muqaffa and Rouzbeh in Persian,(d. 760) was a Persian author and translator in Baghdad. He translated Kalila and Dimna from Pahlavi to Arabic.He was executed on the orders of Al-Mansur the Abased Caliph, for heresy, specifically attempting to import Zoroastrian ideas into Islam.

The main problem of Mukanna's mercury telescope would be achievement of an even rotation with the required period. The focus distance of such lens is calculated by the following formula [7]:L = gT²/ (8p²).
According to this formula, under rotation of liquid lens at speed of 1 turn per 10 seconds its focus distance equals to 12.4 meters. At double increase of rotation speed the focus distance becomes 3.1 meters.

Fig.4. A suitable ancient variants for the mercury telescope. 1- rotating basin with mercury, 2- rotatory stabilizer, 3-weight, a,a',b - flat iron mirrors	Fig.5. An optical scheme of suitable ancient variants for the mercury telescope. 1, 2 -rotating and stationary basin with mercury, 3- iron mirror

 

 

Getting of the evenly rotation of a basin with mercury (1 in fig.1) was quite within power of medieval mechanics.. Mukanna could use devices of a type water or mechanical clockworks. In figure is represented one of suitable variants of a mercury telescope. Energy of a falling cargo (3 on left fig.) here is used. The speed of received rotational movement is adjusted and is stabilized with the help flywheel governor (2 on left fig.).

REFERENCES:

1. Seabrook, W. (1941). Doctor Wood, Modern Wizard of the Laboratory. New York: Harcourt Brace.
2. Abd ar-Rashid al-Bakuvi  "Talhis al-asar vaadja'ib al-malik al kahhar" ("On monuments and miracles of powerful king". In Russian.Мoscow 1971. translated  by Z.Bunyadov  http://www.vostlit.info/Texts/rus2/Bakuwi/text4.htm
   ·  M. de Slane, Catalogue des manuscripts arabe de la Bibliotheque nationale de Paris,          Paris, 1883-1895, p. 393-394, № 2246 (f. ar. 585);
   ·  Georges Vaida, Index generale des manuscrits arabes musulmans de la Bibliotheque nationale de Paris, Paris, 1953, p. 662, № 2246 (arab. 586): «Talhis al-atar fi 'aga'ib al-aqtar»; «Lexicon bibliographicum et encyclopaedicum a Mustafa ben Abdallah Katib Jelebi dicto et nomine Haji Khalfa celebrato compositum», ed. G. Flugel, II, London, 1837, p. 399, № 3589;
   ·  «Die Literatur der Erdbeschreibung bei den Arabern», zusammengetragen von F.Wuestenfeld, Luedde und Berghaus Zeitschrift fuer vergl. Erdkunde, I, Magdeburg, 1842, p. 36, № 109;
3.   "Ibn Hallikan's Biographical Dictionary"
4. Arminius Vambery "About Mukanna"
5. Ella Constance Sykes    "Persia and Its People" 1910   http://bahai- library.com/index.php5?file=sykes_persia_people
6. Bartolemo d'Herbelot "Bibliotheque orientale ou Diction-naire uaiversel, contenant tout ce qui fait connaitre des peuples d'Orient." 1697 . Paris
7.   Thomas Moor  "Lalla Rook"  
8.   N.Likoshina.           http://vostlit.narod.ru/Texts/rus12/Narsachi/text2.htm
9.    Nizam al-Mulk "Siasetname"  Moscow  Akademiya Nauk USSR. 1949. Trans. B.N.Zahoder .            http://vostlit.narod.ru/Texts/rus10/Siaset_name/text5.htm
10.      Marc Frantz, http://www.math.iupui.edu/m261vis/LMirror/mirrorproof.html