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Astron. Astrophys. 325, 1174-1178 (1997)

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5. Evolution of errors of measurement

Fig. 3 shows the evolution over the past three centuries of the error for one measurement [FORMULA] as listed in Table 1. The error diminished by a factor 10 during that time. The diminution is more sensible in the case of the transit timings and is here due to the increasing diameter of the instruments and the use of better pendulum clocks and later chronographs. To obtain a better assessment of the old measurements, experiments have been made according to the original techniques (Toulmonde 1995): (i) duration of transit by projection similar to Mouton's experiments or using a cross-wire placed in a small telescope with a diaphragm of 5 cm; (ii) with the aid of an historical micrometer dated 1677.

[FIGURE] Fig. 3. Representation of error ([FORMULA]) for one measurement of the semi solar diameter
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© European Southern Observatory (ESO) 1997

Online publication: April 28, 1998