How to explain this trajectory of the moon taken from the same spot on Earth over 28 days?


  • Found this picture online, was wondering why the trajectory has taken such a beautiful shape ?


    Related, sort of: https://apod.nasa.gov/apod/ap050713.html We need to know what time(s) the photos were taken.

    The images weren't taken during a single month. According to the image's author (Attributed to Giorgia Hofer Photography) at: https://m.facebook.com/901571186524532/posts/2329156960432607/ The left half comes from January 2017, and the right half of the image contains moonshots taken between July and December 2017. This came up in a previous question that featured the image. https://astronomy.stackexchange.com/questions/32272/struggling-to-understand-the-phases-of-the-moon

    Drat. I *knew* someone was going to spot that! I TOLD them, but would they LISTEN? NO! OK (**) - fine. Neuralyzer batteries charged? Check. Black helicopter fueled? Check. Granola bar in pocket? Check. OK, Tonto - let's ride...

  • James K

    James K Correct answer

    2 years ago

    I don't believe that this can be a simple repeated exposure of the moon.


    On the right, we see a thin crescent, such a moon is only possible when the moon is a couple of days old, and so must be in the West. On the left, we see an old moon, Such a moon is only visible in the very early morning, and that must be in the East, so the image must span nearly 180 degrees.


    But the moon is only 1/2 a degree across, and by my measurement, this makes the image span less than 20 degrees.


    An longer analysis is on reddit https://www.reddit.com/r/Astronomy/comments/9k5gqu/lunar_fake/


    You can get interesting curves like this by recording the position of the moon in the sky at intervals of about a day (or perhaps 24 hr 50 min , since you get the superposition of the moon at a about the same direction, but its height in the sky changes as the moon doesn't orbit around the equator, but in roughly the same plane as the sun. This can be called a lunar annalemma. These have appeared in the astronomy picture of the day https://apod.nasa.gov/apod/ap200507.html and https://apod.nasa.gov/apod/ap050713.html. These images also required some digital manipulation, to bring out narrow crescents taken during the day.


    The reddit user is wrong. The Redditor is correct that the Moon is not the correct size. The creator of the composite photo admitted to expanding the size of the Moon, for artistic purposes. Much of the rest of the Redditor's analysis is plain wrong -- and so is much of this answer. Successive images in the composite photo were take 24 hours and 40 minutes apart rather not the 24 hours and 55 minutes needed to create a lunar analemma.

    @DavidHammen Do you have a reference? As it stands, your comment just says "that person is wrong" without any sort of motivation.

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