ClipArt ETC
"Suppose a to be a stationary celestial object, then as the Earth makes her annual revolution around the Sun S, this object at one time will appear among the stars at e, but six months after, when the Earth comes to the opposite point in her orbit, the same object will be seen at c, the space from c to e being the annual parallax of the object a. But the distances of the stars are so great that the diameter of the Earth's orbit, or 190,000,000 of miles make no difference in their apparent places. Were the fixed stars within 19 trillions of miles, their distance could be told by their parallaxes." —Comstock, 1850

Annual Parallax

"Suppose a to be a stationary celestial object, then as the Earth makes her annual revolution around…

"An arrangement of rings, all circles of a single sphere, intended to show the relative positions of the principal celestial circles."-Whitney, 1902

Armillary Sphere

"An arrangement of rings, all circles of a single sphere, intended to show the relative positions of…

"Originally used for any instrument used for observing stars; afterwards used for an instrument for measurement of altitute; replaced, in modern times, by the quadrant." — Williams, 1889

Astrolabe

"Originally used for any instrument used for observing stars; afterwards used for an instrument for…

"The sextant, an instrument of reflection used by navigators for measuring the altitudes of heavenly bodies."—Finley, 1917

Sextant

"The sextant, an instrument of reflection used by navigators for measuring the altitudes of heavenly…

"A number of rings arranged round a centre, so as to represent a sphere; used to illustrate the relative positions of the ecliptic, equator, etc., of the celestial sphere." — Williams, 1889

Armillary sphere

"A number of rings arranged round a centre, so as to represent a sphere; used to illustrate the relative…