Comment by j1mr10rd4n
1 day ago
To me, this article conflates lunar elevation and phase. Together with the use of ambiguous terms "up", "down", "above", and "below" makes it difficult to understand the author's intent and what their software is meant to visualise.
Lunar elevation (aka "altitude" in celestial coordinates) is sidereal, so the maximum range is determined by the viewer's latitude. The moon's orbital plane is not perfectly aligned with that of the sun-earth so there's another component there, but this only varies +/- 5 degrees of the sun's declination.
Lunar phase is synodic, so there's no significant variation in the observed illuminated portion with the moon's elevation over one night.
The full moon occurs when the moon is on the opposite side of the earth from the sun, so it rises at sunset, transits the meridian at midnight and sets at sunrise, (+/- a few minutes for seasonal variation).
Here's a nice visualisation of the lunar analemna - the figure described by the apparent position of the moon over a month - from Mt. Laguna at 32.8 degrees north. https://www.hpwren.ucsd.edu/news/20250212/
I also found this page with a decent explanation of the apparent effects of orbital cycles. https://www.cyclecalcs.com/learn/synodic-sidereal.html#faq
The strange thing is that there's only visualizations and no photographs! It's not like it's difficult to find the moon to take photos of, nor the sunset.
Or is this a variant of the "counterintuitive" long shadows of mountains at sunrise/sunset? e.g. https://www.fox13seattle.com/weather/skies-erupt-in-color-du... shadow from underneath the cloud layer.
I'm sure I've seen a picture of the long downwards shadow of a mountain on a desert or plain taken from the top with the sun behind the photographer, but the search seems to be sufficiently AI poisoned now :(
I think you're looking for crepuscular rays.
https://en.wikipedia.org/wiki/Crepuscular_rays
A spectacular phenomenon for sure, and I suppose loosely related to lunar phases by virtue of the fact that they both require a very distant source of illumination.
Beautiful picture of Mt Rainier!
I'm sure there are other places that have similar phenomenon, but Mauna Kea often casts great shadows. Here's one with the moon in the cast shadow on the cloud layer below.
https://twanight.org/gallery/inside-the-shadow-of-mauna-kea/
The only place where the illuminated part of the moon points straight down, as the article expects, is also the only place where the sun moves perpendicular to the horizon when setting: if you're at the equator.
Doesn't the sun do this at all latitudes at the equinoxes? (Rises due east, sets due west)
In that time lapse, when the moon is visible, the illuminated portion is always facing “down,” i.e. the horizon?
*analemma