LONGITUDE OF McGlLL OBSBRVATOEY. 



133 



Data from Observations at Montreal. 



Name of Star. 



Time of transit 



over 

 mean of wire: 



Equivalent 

 sidereal time. 



Bb—ii 



Riglit 

 Ascension. 



June 23, 1883. 



a Cephci - - 



^ Aquila? - - 



/3 Cophei - - 



^ Aquarii - - 



11 Cepliei - - 



-■' Cygni - - - 



u Cepliei - - 



79 Draconis 



a Aquarii - - 



tj Aquarii - - 



— Aquarii - - 



^ Pegasi - - 



a Pisuis auslr.- 



a Pegasi - - 



Assumed value of hourly rate of clock —^''.00!*. 



+ 



+ 



+ 



6-.i.l 



6.1 



70.1 



8.4 



70.8 



48.8 



14.1 



73.1 



0.9 



8.2 



0.8 



10.2 



30.2 



14.6 



h. m, «. 



15 7 



15 16 



15 18 



15 22 



15 31 



15 33 



15 38 



15 42 



15 51 



16 1 

 16 10 

 16 2j 

 16 42 

 16 50 



10.87 

 46.42 

 31.05 

 52.82 

 32.13 

 47.45 

 13.93 

 42.92 



2 99 

 54,44 

 31. 41 

 48.08 

 19.13 



2.60 



h. m. 



21 15 



21 25 



21 27 



21 31 



21 40 



21 42 



21 46 



21 51 



21 59 



22 10 

 22 19 

 22 34 

 22 51 

 22 58 



50 03 

 27.02 

 13.10 

 34.43 

 16, .50 

 31.58 

 57.97 

 29 13 

 49.â3 

 42.40 

 20.88 

 40.35 

 13.57 

 5S.62 



7.13 

 6.65 

 7.45 

 6.67 

 7.62 

 7.22 

 6.59 

 7.58 

 6 76 

 6, 61 

 6.68 

 6.95 

 6.50 

 6.71 



I.A.MP WE.ST. 



2.11 

 1.01 

 2.93 

 l.Ul 

 3.04 

 1.52 

 1.02 

 3.45 

 1.00 

 1.01 

 1.00 

 1.02 

 1.16 

 1.0.i 



Eeduction of the Observations. 



For the reduction of the observations, we have the following fundamental equation : 



(1) = [ '/■ + « — n] + Aa + Bb -\-Cc-\- J V. 

 in which : 



7'= the obseivod time over tlio mean of the threads. 



« = ih 0\0207 cos (p sec ô. 



a=z the assumed right ascension of the star observeil. 



a = the azimuth constant. 



h ^ the level constant. 



c = the collimation constant. 



A = sin (<^ — Ô) sec ô = sin .r sec â. 



5 = cos (<p — Ô) sec â = cos î sec rf. 



C = sec d. 



J 7' ^= the error of the cluck at the instant of observation. 



The constant b is always to be taken strictly as a mechanical constant, determined 

 from the readings of the level. It may therefore be incorporated in the known term of 

 the equation. We have therefore : 



(2) = [7'+ n +- Bb—a] + Âa + Ce + JT. 



It i.s always advisable to regard c also as a mechanical constant, if it can be obtained 

 without the reversal of the instrument, or if it can be considered as a constant during the 

 entire series of observations. If the instrument is provided with the two collimators, 

 the value of c can be obtained as often as desired without reversal, and since the value of 

 this constant can be found in this way with much greater precision than by any process 

 which involves a reversal of the position of telescope, equation (1) can, in this case, take 



the form : 



(3) = [(T + « + i?i + Cr) — a'\ + Aa -\- JT. 



in which only a and AT remain to be determined. 



