DIY History | Transcribe | Scholarship at Iowa | Eccentricity of the Sextant by Frederic Furbish, 1893 | Eccentricity of the Sextant by Frederic Furbish, 1893, Page 74

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Eccentricity of the Sextant by Frederic Furbish, 1893

Eccentricity of the Sextant by Frederic Furbish, 1893, Page 74

[page][illegible][/page]

[b?] = refraction (corrected for B and T[subscript]2[/subscript]) In the following figure, let (C') be the center of the graduated arc and (C) the center of rotation of the index arm. Then CC' = ρ and OC'C = θ.

[image of arc PRO [bisected?] to point R from angle point C' ; angle at C' is labeled θ and [half?] that angle is labeled ((1/2)∝') ; an additional point on line C'R has angle labeled C and [half?] that angle labeled ((1/2)∝)]

OCR = OC'R + COC'
PCR = PC'R + CPC'
OCP = OCR + PCR .
= OC'R + COC' + PC'R + CPC'
= OC'P + COC' + CPC' or (1/2)∝ = (1/2)∝' + COC' + CPC' or ε = ∝ - ∝' = 2(COC' + CPC').

     As was explained under "the theory of the sextant" each (1/2) degree on the graduated arc is marked 1 degree. Consequently in order to get the real angle passed over by the index arm or the angle affeted [affected?] by eccentricity we must divide the readings ∝ and ∝' by 2.

     In Δ COC' - sin COC' : CC' : : sin OC'C : OC

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[page][illegible][/page] [b?] = refraction (corrected for B and T[subscript]2[/subscript]) In the following figure, let (C') be the center of the graduated arc and (C) the center of rotation of the index arm. Then CC' = ρ and OC'C = θ. [image of arc PRO [bisected?] to point R from angle point C' ; angle at C' is labeled θ and [half?] that angle is labeled ((1/2)∝') ; an additional point on line C'R has angle labeled C and [half?] that angle labeled ((1/2)∝)] OCR = OC'R + COC' PCR = PC'R + CPC' OCP = OCR + PCR . = OC'R + COC' + PC'R + CPC' = OC'P + COC' + CPC' or (1/2)∝ = (1/2)∝' + COC' + CPC' or ε = ∝ - ∝' = 2(COC' + CPC'). As was explained under "the theory of the sextant" each (1/2) degree on the graduated arc is marked 1 degree. Consequently in order to get the real angle passed over by the index arm or the angle affeted [affected?] by eccentricity we must divide the readings ∝ and ∝' by 2. In Δ COC' - sin COC' : CC' : : sin OC'C : OC