In the book “The occult sciences in Byzantium” in an essay by Maria Papathanassiou titled “Stephanos of Alexandria : a famous Byzantine scholar, alchemist and astrologer” is reported the date of Constantinople’s inauguration.
The survival and continuity of astrology in the Byzantine Empire is evident in a long letter of the emperor Manuel Komnenos (1143-1180) addressed to a monk of the Pantokrator monastery, in which Manuel defends astrology. One of the emperor’s argument was that Constantine the Great (307-337) after consulting the best astrologer of his time, Valens, waited fourteen years for the most favorable date for the inauguration (dedicatio) of Constantinople.
And in the note she adds:
Manuel cites the information which appears in the Byzantine chronicles from the 10th century, that on the fourth day of the dedicatio of Constantinople, Constantine the Great ordered Valens to cast the horoscope of the city and to predict its future. This was done in the year 5838 from the beginning of the world (330 A.D.) on Monday 11 May in the second hour [of the day] and 26 minutes.
The hour of the inauguration of Constantinople was calculated by diurnal unequal hours, that is, by hours obtained by dividing the length of day, from sunrise to sunset, into twelve equal parts. Drawing the inauguration chart is easy if we use the placiadian domification because a house is equal to two unequal or temporal hours. In the ancient time the astrolabe was used to that purpose now we can use our software to set the hourly distance of the Sun in such a way that the part of the diurnal arch already travelled by the Sun is corresponding to two hours and 26 minutes.
The benefic planets, Venus and Jupiter, are rising at the horoscope in Cancer a feminine sign, tropic, watery, horoscope of the world, virtuous, changeable, public, popular, political, fruitful, amphibian. Jupiter is in its exaltation, in sect though occidental. Jupiter is also the ruler of the MC and so in aspect with it. Here Jupiter is the accidental significator of the king and government therefore the ruler of the city is a very good position being Jupiter rising and dignified. Venus is in triplicity and occidental, of mean motion. The Sun is in Taurus a solid, propitious, immutable, industrious sign; in the domicile of Venus and terms of Jupiter. He is also in the acquisitive succedent XI place, house of good fortune. The XI place is traditionally associated with king’s associate, councillors and allies.
The ruler of the Sun, Venus, is dignified as we have already seen. The Moon is Leo, in the Sun’s domicile, in the terms of Venus. She is in the II place meaning the ability to acquire wealth and to be prosperous. Also there is a commutatio between the Sun and the Moon, being the Moon in the domicile of the Sun and the Sun in the exaltation of the Moon. The Sun and the Moon are also natural significators of the king and the people respectively, so their commutatio shows that there is a mutual agreement and harmony between them. Moreover the Sun and the Moon are almost in perfect antiscia and they are in parallel in mundo. In addition the Sun is with the star Aldebaran, of nature of Mars and the Moon is with Regulus, the royal star of nature of Mars and Jupiter.
The malefics are in cadent houses: Mars in XII place in Gemini, peregrine, in conjunction with Mercury; Saturn in the III place, in exile in Leo. The astrologer put them in idle places where they can not harm. The Sun is applying to Saturn with a superior square and since Saturn is the Lord of the VII place, that is, of opponents and enemies of the city, is a good auspice of a secure victory over enemies. Mars, the out-of-sect malefic, is in sextile and parallel of declination with the Moon. Moreover the Moon is applying to Mercury which is in conjunction with Mars showing possible dangers from violence and infighting.
The Pars of Fortune is in trine with the Sun and is squared by Venus. Moreover Venus is on the cusp of the X place from Tyche and Jupiter is also there. Though the Lord of Tyche, Mercury, is not in aspect with it and even if Mercury is in its domicile, is with Mars, showing that the material wealth is not safe from robbery and disputes.
The planetary hour
As we see from the picture below the Lord of the day was the Moon, being Monday and the Lord of the Hour was Jupiter. Since the Moon is also the Lord of the Ascendent of Constantinople and Jupiter is also the exaltation lord of the ascendent it is a further corroboration of the auspicious moment chosen to elect the inauguration of the city.