Micrometer

“The circles for position angle and declination are read by micrometer microscopes illuminated by the lamp L; the scales are illuminated by the lamp l. T is part of the tube proper and turns with the head. The tube V, on the contrary, is attached to the cradle, and merely forms a support for the finder Q, the handles at f and p, and the moving ring P. The latter gives quick motion in position angle; the handles a p clamp and give slow motion in position angle, those at f clamp and give slow motion in right ascension and declination.” —The Encyclopedia Britannica, 1903

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