Stellarium

Find a recurring alignment

Asked by Kevin Flegel

Is there a way for Stellarium to calculate the previous dates of a particular alignment of stars, planets and constellations?

I am interested in finding the dates of when the alignment of the constellation Virgo, the sun, the moon, Mars, Jupiter, Mercury and Venus have aligned the same way as they will on September 23, 2017.

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gzotti (georg-zotti) said : 		#1

There is no such function available, and you will probably have a hard time looking for the "same" alignment, depending on what you consider "same".

Given the Moon's Meton cycle of 19 years and a Venus recurrence cycle of 8 years, start with a period of 152 years to have sun, moon and Venus in similar positions, then check the other objects. I am not aware of practically useful geocentric periods for the other objects to find a smallest common multiple. Even in these 152 years, stars of Virgo (and all other stars) will have drifted by about 2 degrees in ecliptical longitude due to precession.

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Kevin Flegel (kevin-flegel) said : 		#2

Thank you for your answer.
I didn't think there was a simple way.
Given the mathematics, it looks like it would be quite a long time.