The Moon’s orbit is tilted at 5°8' to the ecliptic.

What is the lowest latitude from which the Moon may never set (the Moon’s “arctic circle”)?

The maximum height of the ecliptic above the equator
is ε = +23°24'.
The Moon can get 5°8' above this, i.e. up to +28°32'.
So the Moon's maximum declination is +28°32'.

An object of declination δ will be circumpolar
at latitude 90°-δ,
i.e. at latitude 61°28'.

So if the Moon is at its greatest possible declination,
it appears circumpolar from any latitude north of 61°28'N.
(The northern tip of Shetland is at latitude 60°52'.)

Would the Moon always be circumpolar, at this latitude?

No; only at a “major standstill”.

Sometimes the Moon’s orbit will be inclined the other way to the ecliptic,
and it will reach a maximum height of only 23°24' - 5°8' = 18°16'.

This is a “minor standstill”.

(The interval between major standstills is 18.6 years.

Back to "ecliptic coordinates".