. Astronomy for high schools and colleges . 82 ASTRONOMY. the same as that of {n—1) parts on the divided hmb M iVor the reverse. The first stroke a is the zero of the vernier, and thereading is always determined by the position of this zeroor pointer. If this has revolved past exactly twenty di-visions of the circle, then the angle to be measured is20 X ^j ^ being the value of one division on the limb{N M) in Fig. 34.—the vernier. Call the angular value of one division on the vernier d\ (n — l)d = nd\ord = d,SiTidd—d=-d; d — d\^ called the least count of the vernier which is onen*** part
. Astronomy for high schools and colleges . 82 ASTRONOMY. the same as that of {n—1) parts on the divided hmb M iVor the reverse. The first stroke a is the zero of the vernier, and thereading is always determined by the position of this zeroor pointer. If this has revolved past exactly twenty di-visions of the circle, then the angle to be measured is20 X ^j ^ being the value of one division on the limb{N M) in Fig. 34.—the vernier. Call the angular value of one division on the vernier d\ (n — l)d = nd\ord = d,SiTidd—d=-d; d — d\^ called the least count of the vernier which is onen*** part of a circle division. If the zero a does not fall exactly on a division on thecircle, but is at some other point (as in the figure), for ex-ample between two divisions whose numbers are P and(P + 1), the whole reading of the circle in this position isP X (^ -H the fraction of a division from P to a. If the m}^ division of the vernier is in the prolongationof a division on the limb, then this fraction P a is m THE MElilDlAN CIRCLE, 83 (d -^d) = -d. In the figure n = 10, and as the 4tli division is almost exactly in coincidence, m = 4, so that the whole reading of the circle \^ P X d + -r^- d. If <? is 10, for example, and if the division P is numbered 297°40, then this reading would be 297° 44, the least countbeing 1, and so in other cases. If the zero had started fromthe reading 280° 20, it m
Size: 1588px × 1572px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1880, bookpublis, booksubjectastronomy
