As observed from the surface of Earth: Will the moon ever repeat the same path (trajectory)? If yes, what is the period of repetition? And also will the moon cover the night sky with its path completely over a period of time?

More explanation: I was observing the moon from my window and I was wondering will the moon follow the same path (trajectory) as it did before, and if I am taking photos all the different positions of the moon over a long period of time will it have covered the night sky?

  • $\begingroup$ To clarify, are you asking about the apparent motion of the moon due in part to the rotation of the Earth (in which the trajectory of the moon takes it across the sky every day), or the trajectory of the moon relative to the stars (in which the motion of the moon takes about one month) $\endgroup$
    – James K
    Commented Mar 17, 2019 at 7:41
  • 1
    $\begingroup$ The moon remains within a few degrees of the ecliptic, so can never cover the entire night sky. For example, the moon can never be near the North Star. $\endgroup$
    – user21
    Commented Mar 17, 2019 at 16:59

1 Answer 1


There is a beautiful composite picture demonstrating exactly this over at http://www.twanight.org/

enter image description here

This is a composite of 90 photos across the four days, so you can easily see how far the moon moves each day (about 13 degrees)

From https://cseligman.com/

on average the Moon crosses the sky once every 24 hours and 49 minutes (53 minutes longer than the stellar "day"). As a result, it rises (and sets) later and later every day, until after about 27 days, when it has gone once around the sky relative to the stars, it is back in its original position, rising and setting at its original time(s).


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