Todays Biue Moon (that wont happen again til 2036) is the biggest brightest and closest the moon is to Earth Im trying to determine how it appears at ones given latitude.Obviously the closest one is to the equator the larger and brighter it should appear. I asked Google but could not find a formula to determine the thickness of the Earth by horizontal cross section at a given latitude. Those show the distance from a given latitude to the Earths center as clearly indicated by their nearly uniform measurement whether from the equator or the poles!

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    $\begingroup$ Can you clarify your question? Perhaps add a sketch that shows the dimension you want to know. Since the Earth's diameter is 12800 km and the Moon's distance is 384000 km, the change in size due to location is small (on the order of 3%). $\endgroup$
    – JohnHoltz
    Aug 31, 2023 at 21:33
  • $\begingroup$ Note: blue moons occur about every 29.5 months on average... the next blue moon is May 2026. There's won't be another blue "supermoon" until 2036. Not that most people can tell that ~3% difference between a supermoon and a regular or "inferior" ("infra?") moon anyways. (Talking about monthly supermoons, not seasonal ones, the more old-style meaning) $\endgroup$ Sep 3, 2023 at 17:54

1 Answer 1


Method 1:


You know the Radius of the earth and the lattitude kindof, you can convert the lattitude using Sin or Cos function.

Method 2:

Rhumb line tool online, because parallels are rhumb lines:


if you have a 1/2 or a full rhumb circle of a parallel using the GSM ellipsoid/spheroid, then you just need to know the radius.

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    $\begingroup$ Please add the relevant content to your answer. "Link-only" answers deprecate quickly and are better suited for comments. $\endgroup$
    – f.thorpe
    Sep 3, 2023 at 16:10
  • $\begingroup$ Just my luck. The wiki page to the sine and cosine page is down! $\endgroup$
    – JohnHoltz
    Sep 4, 2023 at 0:28
  • $\begingroup$ Sorry the link was SVG and stack refused to upload it. if the server is down, copy paste the image name: Sinus_und_Kosinus_am_Einheitskreis_1.svg $\endgroup$ Sep 4, 2023 at 10:31

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