ASTRONOMY: A. VAN MAANEN 
135 
given in table 2, whose successive columns contain the plate numbers 
of the pair, the difference in the parallax-factors, the difference in the 
factors for annual proper motion, the result of the measures (in 0.0005 
of a revolution of the micrometer screw as unit), the residuals, and the 
difference in the hour angles. 
Eight comparison stars were used; Table 3 gives their brightness, 
their co-ordinates in right ascension and declination, and their relative 
parallaxes with the probable errors of these parallaxes. 
TABLE 2 
MOR.-EV. 
Ap 
Aw 
M 
V 
At 
1061- 758 
+ 1.29 
+0.74 
+29 
+ 15 
-]?0 
1062- 749 
+ 1.27 
+0.75 
+ 3 
-11 
+0.7 
1079-1163 
+ 1.38 
-0.28 
+ 13 
- 6 
-1.0 
1050- 759 
+ 1.42 
+0.71 
+20 
+ 3 
-3.0 
1080-1126 
+ 1.12 
-0.21 
+ 8 
- 6 
0.0 
1063- 750 
+ 1.27 
+0.75 
+ 10 
- 4 
-1.8 
1081-1143 
+ 1.37 
-0.28 
+31 
+ 13 
+3.7 
1082-1127 
+ 1.12 
-0.21 
+ 10 
- 4 
+6.3 
TABLE 3 
COMP. STAR 
Br 
X 
y 
TT 
p. E. 
1 
bf 
+0.7 
+0.'4 
+0V019 
±0'.'010 
2 
bf 
+4.1 
+2.1 
- 3 
6 
3 
f 
+2.9 
-2.3 
2 
9 
4 
f 
+ 1.5 
-2.2 
- 11 
8 
5 
f 
-0.5 
-3.3 
+ 11 
7 
6 
f 
-2.3 
-1.8 
- 1 
14 
7 
f 
-3.0 
+2.5 
- 24 
9 
8 
bf 
-2.9 
+5.1 
+0.014 
±0.005 
The material in Table 2 gives the following normal equations for 
the determination of the parallax of the nebula: 
+ 2.41m« + 2.61x = + 28 
+ 2. 61m,, +13.187r = +161 
From these 
7r.ei. = +12.7 = +0^.021 ±0".004 
Ma = - 2.1 = -0".003 =1=0". 008 
Only one other determination of the parallax of this nebula is avail- 
able, viz., that by Wilsing."^ His material comprised 31 plates, taken 
with the 80-cm. photographic refractor at Potsdam. His conclusion 
was that the parallax of N.G.C. 7662 cannot be larger than O'M or 0".2. 
