Trying to find a word similar to apex but ending with -muth
Solution 1:
You're probably thinking of azimuth, but that's simply a direction at a particular angle.
The direction of a celestial object from the observer, expressed as the angular distance from the north or south point of the horizon to the point at which a vertical circle passing through the object intersects the horizon.
[ODO]
The highest point in the sky, similar to apex, is zenith.
The point in the sky or celestial sphere directly above an observer. The opposite of nadir.
[ODO]