Elements of theoretical and descriptive astronomy, for the use of colleges and academies (1901)
White, Charles J · New York: J. Wiley & sons · leaf 51
et the lines AD andBChe drawn perpendicular to the reflecting surfaces, and pro-long AD until it meets BO. The angle DOB is equal to theangle which the two surfaces make with each other. We havethen to prove that the angle SEB is double the angle DOB. Now since the angle of incidence always equals… … Fig. 16. we wish to measure the angular distance between two celestialbodies, A and B (Fig. 16). The instrument is so held that itsplane passes through the two bodies, and the fainter of them, which in this case we suppose tobe By is seen directly through thehorizon-glass and the telescope.B is so…
Astronomy
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