Ptolemy explained that by using astronomical calculations based in part on eclipses, “we have derived to compute back to the beginning of the reign of Nabonassar, ” the first king on his list.Thus, Christopher Walker of the British Museum says that Ptolemy’s canon was“ an artificial scheme designed to provide astronomers with a consistent chronology ” and was “not to provide historians with a precise record of the accession and death of kings. ”
اوضح بطليموس انه اجرى حسابات فلكية ،‏ معتمدا جزئيا على خسوفات القمر ،‏ « ليحتسب متى بدأ مُلك نبونصر » ،‏ الملك الاول .‏