740 EAEL OF EOSSE ON THE CONSTEUCTION OF SPECULA OF 6 -FEET APEETUEE, 
From the preceding observations the following coordinates, X, Y, with regard to a 
have been deduced. X is the coordinate in the direction of .4R, or A/fl cos S ; Y is the 
coordinate in declination or A^. In this deduction, where the angles of position of any 
star were taken from three different points previously fixed, I have combined only those 
two directions which promised the most exact evaluation of the coordinates. Thus, 
for instance, the star r is related to e and s. In the three triangles formed in this 
way, the angle at r is found respectively Zre=91° 24', Zrs=137° 54', 5re=130° 42'. 
Hence it is eHdent that the nearly right-angular intersection of the two sides I r and r e 
in the triangle Ire^ must give the best combination for the deduction of the position 
of r. The relation of I and e to another and to a being previously established, the 
coordinates of y to a were deduced from the resolution of the triangle Ire. The 
difference of these coordinates from the corresponding previously fixed coordinates of s 
with regard to «, gave the angle of position of r from s by calculation =258° 37'. This 
calculated angle, compared with the directly observed position =258° 18', shows a differ- 
ence of only 19', and bears, therefore, a very satisfying testimony to the exactness of the 
deduced position of r. The same proceeding having been followed in all other cases, 
where control observations had been made, I have got the conviction that the probable 
error in any of the following coordinates will be considerably inferior to one second of 
space. It will be comparatively smaller for the brighter stars, but somewhat greater for 
the very faint objects. 
Calculated Coordinates of the Observed Stars with regard to a. 
X. 
Y. 
q 
- 97'G 
- 20-9 
a! 
- 12-3 
— 57-2 
h 
+ 21*6 
+ 199-7 
o 
+ 49-6 
+ 144-0 
p 
+ 60-6 
+ 57-9 
d 
+ 152-5 
+ 12-8 
e 
+ 172-5 
+ 98-8 
9 
+ 174-3 
+ 191-5 
f 
+ 174-6 
+ 142-2 
k 
+ 186-8 
— 121-0 
n 
+ 224-9 
-184-7 
m 
+ 225-0 
— 164-3 
i 
+ 238-2 
+ 71-5 
h 
+ 251-1 
+ 101-7 
z 
+ 279-6 
-199-7 
V 
+ 308-3 
+ 186-3 
w 
+ 317-7 
— 102-0 
c 
+ 321-1 
+ 62-8 
y 
+ 321-8 
-219-5 
i 
+ 332-4 
— 162-2 
t 
+ 347-8 
— 128-9 
V 
+ 390-7 
-161-7 
r 
+ 396-9 
- 74-0 
u 
+ 402-4 
— 200-8 
X 
+ 442-0 
— 148-5 
s 
+ 555-8 
• — 42-0 
Pulkom., Feb. 4, 1852.] 
(Signed) 
Otto Struve. 
