What are the aspects does the moon (astronomical position and other astronomical aspects) differs between cities located in the same latitude? - For example: Seattle, Munich, Vienna, and Ulaanbaator are on the same line, If there are four persons see the night sky at the same time: the sky view (constellations) will be the same because they all on the same latitude; but Does the moon position and movement and the time of rise and set, will be exactly the same?

  • Could using ephemeris of the moon calendar (Ascension, declination, culm, Constellation ...etc) help to know the differences? and Which aspect is the most obvious one?
  • $\begingroup$ When you say "same date", do you mean that these pictures are taken at the exact same time, or that they are taken at the same local time (but hours apart due to time zones), or that they are taken at some point on the same local calendar day, at an unspecified time on that day? $\endgroup$
    – notovny
    Jul 8, 2021 at 16:31
  • $\begingroup$ Is this an academic exercise or is there something you want to achieve with actual photos? There are some complications related to "photos" of the moon due to the limitations of dynamic range & exposure on current cameras. If the camera is set to expose for the moon (avoid over-exposure) then typically the stars are too faint to show up in the image. In other words, use of background stars may not work if the exposure isn't long enough. $\endgroup$ Jul 8, 2021 at 18:26
  • $\begingroup$ same astronomical time, same calendar date $\endgroup$
    – huab
    Jul 8, 2021 at 19:05
  • 1
    $\begingroup$ I used to contrast two photos in same day but different cities , but really altitude is most contrasted between cities, and cities tropical zone is most equals in all , only change shadow, but is only by hour $\endgroup$
    – Adrian R
    Jul 8, 2021 at 19:28
  • 1
    $\begingroup$ @Fred my question is to the OP, checking to see if I understand the question. No, I didn't mean that, I mean at the same time literally. But they could mean the same time locally as well, thus the request for clarification. I think "the same time" without adding "locally" should be understood to be essentially the same as "simultaneously", but you are right there is wiggle room, so it should be nailed down by the OP, or alternatively an answer should simply address both cases. $\endgroup$
    – uhoh
    Jul 10, 2021 at 5:59

1 Answer 1


If images taken at same time (UTC), the Moon would be at different altitudes in sky, for some locations it would be below horizon. Next there would be a small shift of Moon with respect to stars in background. This is a parallax effect. There are observing projects that measure this during total lunar eclipses. Smallest is a bit of extra east-west libration i.e. You see a bit more round the edge of the Moon on the side (east /west) nearer (angle-wise) to the observer. You could do a demo with a sphere with some pattern on it, move side to side and you'll see slightly different faces of the sphere. Software like Virtual Moon Atlas have a setting for the location of the observer, and to switch location to center of earth (geocentric), or at location (topocentric), and a switch to turn on/off libration. Experiment with your cities.

At same local time, gets way more complex because the Moon and Earth have moved in their orbit between the 2 observations. So different phases, librations from orbital position, plus effects mentioned above.


You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .