Draconite period

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The draconian period refers to the time a satellite has between repeatedly passing the same junction .

The name is derived from dragon point ( Latin draco ), the old word for the lunar knot .

Draconite Month

For the earth's moon , the mean value of the time periods between two passes through the same lunar node is called the draconian month . A lunar eclipse is only possible when one of the two lunar nodes with a full moon meets, and a solar eclipse when the new moon meets . Therefore, the draconian month is used to calculate the Saros period (the period after which solar and lunar eclipses repeat).

Draconite year

A drakonitisches year is - at least for the earth - not specified: An average value can not be defined because the ecliptic , the average level of the earth's orbit and thus no "nodes of the Earth's orbit" exist. In fact, the earth's true orbit deviates from the ecliptic, and the "node of the earth's orbit" is the true vernal equinox , the corresponding period the solar year .

For the other planets, on the other hand, a draconian year could very well be specified - in the extended sense of the year term as orbit period - since their inclination with respect to the ecliptic, unlike that of the earth, is different from zero . But because the draconian period is mainly to be seen in connection with eclipses and these do not occur with the other planets, but only occultations and passages, the indication of a draconite year for the other planets is not of particular interest.

See also