# Tips of Crescent

Can it be shown mathematically that the line connecting tips of crescent is parallel to the North-South line and the line gives latitude of the plane ( When the Moon is sufficiently close to the horizon, we can approximate the surface of sky as a simple plane.)

Sources :

https://www.naturalnavigator.com/find-your-way-using/moon/

• I think yes it can, perhaps faster in Math SE than here if you need a proper mayhematical proof.
– uhoh
Jan 1, 2022 at 9:11
• They said it's off topic there math.stackexchange.com/questions/4346311/tips-of-crescent Jan 1, 2022 at 9:30
• Here's a related question on our sister site: physics.stackexchange.com/q/6969/123208 Jan 1, 2022 at 9:38
• @Particleking ya it seems two long-time users mentioned that. Okay let's see what we can do here!
– uhoh
Jan 1, 2022 at 10:39

They don't. In this image (from 28th Dec 2021) the blue grid represents lines on an equatorial grid. The lines that run from top right to bottom left are North-South lines. The tips of the crescent very clearly don't point to the North.

The moon is lit by the sun and both the sun and the moon are in the plane of the ecliptic (to within a few degrees). So, as the "bulge" of the crescent points towards the sun, and along the ecliptic, The tips of the crescent will point towards the ecliptic pole which is about 23 degrees away from North.

However since the moon is not exactly on the ecliptic even this is not exactly correct, and close to new moon the tips of the moon could point almost anywhere (think how the invisibly thin cresent will rotate as the moon passes the sun on a new moon at which there is no eclipse.)