Peck, William G. (William Guy), 1820-1892 · New York, Chicago, A. S. Barnes & company · leaf 26
mage of a star is seenat the intersection of the cross-hairs, the star itself must bein the prolongation of the line of collimation, for the ray oflight that coincides with the line of collimation passesthrough the objective without deviation. In the transit instrument, yet to be described, the… … Fig. 6. The reticle. and is sometimes double. The wires at right angles to dcare equidistant and usually either 5 or 7 in number, themiddle one, ab, intersecting the hori-zontal one, dc, in the line of colli ma-tion. At whatever elevation the lineof collimation may be set, the middlewire of the…
Astronomy
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