What's the noun for equatorial? Here's the word you're looking for.
equator
(Equator) An imaginary great circle around the Earth, equidistant from the two poles, and dividing earth's surface into the northern and southern hemisphere.
(astronomy) A similar great circle on any sphere, especially on a celestial body, or on other reasonably symmetrical three-dimensional body.
“Let L be the earth's equator and let x be a point in the northern hemisphere.”
“From the equator she will sail past the Cape of Good Hope and then to Cape Leeuwin in Australia.”
“Easterly winds predominate near the equator and also in the lower atmosphere at the poles.”
equatorial
(astronomy) 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.
