What do the phrases "Moon rides high...

As the equator wraps around Earth, so the celestial equator wraps around the sky. It runs in an arc from east to west, passing low in the south; the farther north one stands, the lower it passes. When the Moon runs low in the sky, it is the farthest beneath this equator. If you live sufficiently far north, it will never rise above the horizon at night. Similarly, the Moon will be unusually high in the sky when it rides high.