. Astronomy for students and general readers . val to 7= May 25. 1 !? 13 12-6, T — r„ = 13 1113 12-6= 13-467. Hence we have A 2„ = - 16 18-50 dT(T- r„) = + 1 5-03 A r= 15 8-4r T= 11 13 12-60 r = J0~58^^i3 But in this example the rate is obtained for one true sidereal day,while the unit of the interval 13-467 is a sidereal day as shown bythe clock. The proper interval with which to compute the rate inthis case is 13 10 58 4-18 = 13-457, with which we tind A r„ = — 16 13dT X 13-457= + 1 4« A r = — 15> 82= 11 13 12 T = IC- 58 4 5098 5260 08 This repetition will be rendered unnecessary by alway
. Astronomy for students and general readers . val to 7= May 25. 1 !? 13 12-6, T — r„ = 13 1113 12-6= 13-467. Hence we have A 2„ = - 16 18-50 dT(T- r„) = + 1 5-03 A r= 15 8-4r T= 11 13 12-60 r = J0~58^^i3 But in this example the rate is obtained for one true sidereal day,while the unit of the interval 13-467 is a sidereal day as shown bythe clock. The proper interval with which to compute the rate inthis case is 13 10 58 4-18 = 13-457, with which we tind A r„ = — 16 13dT X 13-457= + 1 4« A r = — 15> 82= 11 13 12 T = IC- 58 4 5098 5260 08 This repetition will be rendered unnecessary by always giving the ratein a. unit of the clock. Thus, suppose that on June 3, at 4 11 12--35by the clock, we have found the correction -I- 2i 10-14; and onJune 4, at 14 we have found the correction + 2 19-89;the rate in one hour of tie dock will be ^=^04=+°-^«^«- U ASTJiOAOMY. % 4. THE TRAIfSIT nsrSTHUMEIfT. The meridian trcmait instrument, or Lriefly tlie tran-sit, is used to observe the transits of the heavenly Fig. 28.—a transit rNSTKUMENT. and from the times of these tra:nsits as read from theclock to determine either the corrections of the clock orthe right ascension of the observed body, as explained inChapter I., §5. THE TRANSIT INSTRUMENT. 75 It lias two general forms, one (Fig. 28) for use in lixelobservatories and one (Fi^. 29) fornse in tbe field. It consists essentially of a telescope T T (Fig. 28)mounted on an axis V Fat right angles to it.
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