The present book contains Euclid 's astronomical work " Phenomena ", hitherto unknown in Greece, which focuses, as its title indicates, on phenomena that occur during the movement of the celestial sphere. It is no exaggeration to say that " Phenomena " is a "living" study, since the admission of the celestial sphere, even today, serves practical purposes.

This work of Euclid is presented in two variants, and the ancient Greek text comes from the respective codices of the National Library of Paris and the Vatican Library. However, the ancient text from the edition of A. Nokk "Euclidis Phaenomena" (Freiberg), Berlin 1850 was also used.