98 7 On the observations of Comets. 
For the first observation we have 
True R.A. True Declin. 
Arcturus, 211° 51-36” ec To ai” 
a Lyra, 277 42 50 38 37 25 
To correct the distances, it is necessary to know the alti- 
tude of the comet. This may be found, first by the globe, 
and afterwards: when the Right Ascension and Declination 
are ascertained, the altitude may be calculated correctly, 
ene if very different from the assumed, the distances 
ould be corrected again with it. We will su supper then, 
is apparent altitude of the comet 5° 19’. 
The latitude of the place of observation was 39° 59 30” 
N. With this, the altitudes of the stars corresponding to 
the time, will be found by calculation. 
Apparent altitude of Arcturus, 48° 57 
Apparent altitude of o Lyra, 71 45 
With these data we find for the first distance dD=6' 58” 
and for the second dD=9’ 8”. Therefore the true distances 
will be 
True distance to Arcturus, §2°°13': 98" 
True distance to « Lyra, 90 41 38 
Let c (fig. 1.) be the comet, @ Arcturus, and 6 the other 
star. In the triangle pab, the side ab will be found equal to 
59° 0’ 44”, and the angle pab=56° 15’ 46”. In the triangle 
cab, — three sides being given, the angle cab will be found 
=95° 31° 27" from which subtracting the angle pab, it will 
remain ee 15’ 41". Now, in the triangle Pea, know- 
ing the sides pa and ca, and the poe cap, the side ep will 
found=39° 55’ 41”, and the angle cpa=102° 19’ 16”. 
Subtracting cp from 90°, and cpa fom the Right Ascension 
of Arcturus, we shall have ; 
of the comet. . Declin. of the comet. 
July 10th, at 9% 39’ 48” bee 32’ 20” 50° 4 19" N. 
Supposing 1’ of error in each of the distances. observed 
formula 1 gives dr=34" 8, which being —-, in formu- 
las 2 and 3, these give dv=50" 6 and dw= — 
