A Draconic month, or nodical month is the average number of days it takes the Moon to cross the ecliptic, twice.
A Draconitic month is slightly shorter than the sidereal month, 27 days 5 hours, 5 mins, 35.8 seconds.
The nodes precesses over a full circle in about 18.6 years.
The significant, eclipse causing nodes occur twice each year when the moon is very close to the ecliptic and passing in front of the sun.
Each node provides the possibility for an eclipse, but it will probably not be visible where you are!
Why is this called a Draconic cycle?
It is difficult to see how the image of the snake (Draco) and the two bears have anything at all to help someone determine where the Moon is in relation to a node...Perhaps a star in Draco, was used to check how the position of the moon on the ecliptic?
The Ecliptic pole is within Draco, and I've seen old pictures of lines of latitude drawn from the Ecliptic Pole. If this is significant or not I've yet to make up my mind!
The answer seems to be: The serpent causes eclipses.
A Draconitic month is slightly shorter than the sidereal month, 27 days 5 hours, 5 mins, 35.8 seconds.
The nodes precesses over a full circle in about 18.6 years.
The significant, eclipse causing nodes occur twice each year when the moon is very close to the ecliptic and passing in front of the sun.
Each node provides the possibility for an eclipse, but it will probably not be visible where you are!
It is difficult to see how the image of the snake (Draco) and the two bears have anything at all to help someone determine where the Moon is in relation to a node...Perhaps a star in Draco, was used to check how the position of the moon on the ecliptic?
The Ecliptic pole is within Draco, and I've seen old pictures of lines of latitude drawn from the Ecliptic Pole. If this is significant or not I've yet to make up my mind!
The answer seems to be: The serpent causes eclipses.
"Renowned scholars in this science [astronomy] say that eclipses and occultations of the stars take place because of the Snake (Atalia). In order to confirm their words they draw a similar figure and say that the Serpent (Atalia) has a body shaped as a serpent, so often it is called the dragon and snake. The width of its body is 24 degrees and the length is 180 degrees, ie six Zodiacal signs, or half of the sphere, so you can immediately see that its head and its tail are face to face and diametrically opposed. This Snake (Atalia) always walks in the Zodiacal signs, his head in one, its tail in the other. The center of its body is outside the crown all the signs of the Zodiac, toward the North, on the side of the Chariot, because it is curved and is shaped like a semicircle, like an arc... Its movement takes place, differently from planets' one, not from West to East, but as the twelve signs' motion, from East to West. It moves of 3'11'' in a a day and a night, 1° 33' in a month, and 19° 20' in a year. It therefore makes a complete revolution in 18 years, 7 months and 16 days. Since the Snake is under the Sun and the Moon, whenever the Moon is in conjunction with the Sun in the sign and the degree where is the head of the Snake (Atalia) or its tail, the Serpent (Atalia) stays ahead the Moon and so hides the Sun...." Reference: Of the judgements on the lunar nodes written by Lucia Bellizia translated from Italian into English by Margherita Fiorello)
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