A manual of spherical and practical astronomy, embracing the general problems of spherical astronomy, the special applications to nautical astronomy, and the theory and use of fixed and portable astronomical instruments, with an appendix on the method of least squares . volving arm to which are attached the small mirror w, the^ ? telescope T, and the ver- nier, or index H; M thecentral mirror which isrevolved by the arm 311,carrying the vernier, orindex /. In accordancewith the nomenclature innautical works, we shallcall H the horizon index,and /the central index. The arc is graduatedfrom 0° t
A manual of spherical and practical astronomy, embracing the general problems of spherical astronomy, the special applications to nautical astronomy, and the theory and use of fixed and portable astronomical instruments, with an appendix on the method of least squares . volving arm to which are attached the small mirror w, the^ ? telescope T, and the ver- nier, or index H; M thecentral mirror which isrevolved by the arm 311,carrying the vernier, orindex /. In accordancewith the nomenclature innautical works, we shallcall H the horizon index,and /the central index. The arc is graduatedfrom 0° to 720° in the di-rection HIE. Let A and B be the objects whose angular distance is to bemeasured. First: let the central index / be clamped at anyassumed point of the arc. Bring the plane of the instrument topass through the two objects. Direct the telescope towards theright hand object B, and, without touching the central index,move the horizon index H (or rather revolve the instrument,keeping the telescope bearing on B), until the image of the lefthand object A is reflected from the central mirror 31 to thehorizon glass m, and thence to the eye, and thus into coincidenceUith the object B seen directly. This completes the first part of the observation. Now,. Fig. 29.
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Keywords: ., bookcentury1800, bookdecade1, booksubjectastronomicalinstruments
