The few ancient sources we have regarding him agree that he came from the small island of Tenedos, some 6 kilometres off the coast of northwestern Anatolia. They also suggest that he wrote a poem called, Astrologia, a work probably dealing with astronomical (and perhaps meterological) phenomena such as the rising and settings of stars.
The C4th BCE historian of philosophy, Theophrastos (On Signs 1.4), says that he observed the (probably winter) solstice in Tenedos using Mount Ida as a reference point on the horizon. This is certainly possible since the 1770 metre peak of Mount Ida lies about 70 kilometres to the east southeast on the mainland, and is visible from Tenedos on a clear day. However, such an observation, if it was an attempt to determine the date of the solstice (a likely supposition), would not have been very accurate, since a movement of just one degree in azimuth of the Sun on the horizon takes eighteen days to accomplish around the time of the solstice. Therefore, it would have required systematic observations over a period of perhaps a month to try and determine by interpolation the day on which the Sun rose in the most southerly position.
The C3rd CE Roman writer Censorinus says that he devised the octaeteris (On the Day of Birth 18.4–6):1
But this space of time, which only coincides with the course of the sun and not with that of the moon, was again doubled; and it was called octaeteris (a cycle of eight years) then called euneæteries (a cycle of nine years) because this new year returned on the ninth year. This period of time was considered throughout nearly all of Greece, as the real Great Year, because it is composed of years without any fraction, as all Great Years should be. In effect, this was composed of eight full years and 99 full days. The institution of this octaeteris is generally attributed to Eudoxus of Cnidus, but it is said that Cleostrates of Tenedos was the first to invent it, and after him came 22 others who, with the aid of different intercalations of months, have each composed an octaeteris. Thus Harpalus Nauteles, Mnesistratus and others calculated such periods; amongst them Dositheus, whose work is called the Octaeteris of Eudoxus. It is from this cycle that in Greece many religious festivals were celebrated with great ceremony. At Delphos, the games called Pythian were anciently celebrated every eight years.If this is true, it shows that the calendar was a focus of interest for Kleostratos and his observation of the solstice would be a part of this.
Beyond this, little detail about his other achievements is known. With regard to the zodiac, our main source is the C1st CE Roman writer Pliny the Elder (never a great sign) who says this about him (Natural History 2.8):2
The account of the circles of the heavens will be better understood when we come to speak of the earth, since they have all refer to it; apart from what has been discovered about the one carrying the zodiacal signs. Anaximander the Milesian, in the 58th Olympiad, is said to have been the first to have opened the door to the subject, by making out its obliquity, and then Cleostratus made out the signs in it, the first parts of Aries and Sagittarius —Atlas having made out the sphere itself long before.The 58th Olympiad was the period 548–545 and thus Kleostratos must have been active after this. The difficulty here is that Pliny's statement is difficult to comprehend. At the very least it seems clear that he had something to do with the establishment of the zodiac in Greece, and possibly he redefined or reapportioned the stars at the begining of Aries and Sagittarius.
Lunar Crater: Cleostratus (diameter 63 km).
NOTES
1. Hoc quoque tempus, quod ad solis modo cursum nec ad lunae congruere videbatur, duplicatum est et octaeteris facta, quae tunc enneaeteris vocitata, quia primus eius annus nono quoque anno redibat. Hunc circuitum vere annum magnum esse pleraque Graecia existimavit, quod ex annis vertentibus solidis constaret, ut proprie in anno magno fieri par est. Nam dies sunt solidi IIdccccxxii, menses solidi uno minus centum, annique vertentes solidi octo. Hanc octaeterida vulgo creditum est ab Eudoxo Cnidio institutam, sed alii Cleostratum Tenedium primum ferunt conposuisse et postea alios aliter, qui mensibus varie intercalandis suas octaeteridas protulerunt, ut fecit Harpalus, Nauteles, Menestratus, item alii, in quis Dositheus, cuius maxime octaeteris Eudoxi inscribitur. Ob hoc in Graecia multae religiones hoc intervallo temporis summa caerimonia coluntur; Delphis quoque ludi, qui vocantur Pythia, post annum octavum olim conficiebantur. Proxima est hanc magnitudinem quae vocatur dodecaeteris ex annis vertentibus duodecim.
2. Circulorum quoque caeli ratio in terrae mentione aptius dicetur, quando ad eam tota pertinet, signiferi modo inventoribus non dilatis. obliquitatem eius intellexisse, hoc est rerum fores aperuisse, Anaximander milesius traditur primus olympiade quinquagesima octava, signa deinde in eo Cleostratus, et prima arietis ac sagittarii, sphaeram ipsam ante multo Atlas.
Last updated 17/05/20
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