Origin: Latin suffix -al
Equatorial has 6 different meanings across 2 categories:
a telescope whose mounting has only two axes of motion, one parallel to the Earth's axis and the other one at right angles to it
"The astronomer adjusted the equatorial mount so that its polar axis aligned perfectly with the North Star for smooth tracking."
A kind of telescope mounted so as to have two axes of motion at right angles to each other, one of them parallel to the axis of the Earth, and each carrying a graduated circle, one for measuring declination, and the other right ascension, or the hour angle, so that the telescope may be directed, even in the daytime, to any star or other object whose right ascension and declination are known.
"The observatory director adjusted the equatorial telescope to track the bright morning star with precision despite the rising sun."
In plain English: Equatorial is not actually a noun; it is an adjective that describes something located near Earth's middle belt where day and night are about equal length every day of the year.
"The equator is an imaginary line that divides the Earth into northern and southern hemispheres."
of, near, or relating to the equator
"The equatorial regions receive the most direct sunlight throughout the year."
In plain English: Equatorial describes anything related to an imaginary line around Earth's middle that divides it into northern and southern halves.
"The equatorial regions receive direct sunlight year-round due to their location near the middle of the Earth."
Usage: Use "equatorial" exclusively when describing locations, climates, or objects situated on or near the Earth's equator. Do not confuse this adjective with unrelated telescope terminology that shares similar roots but refers entirely different astronomical instruments.