i88 
RESEARCHES IN STEELAR PHOTOMETRY 
For comparison, in the three parts of the Potsdam catalogue the probable errors 
of the mean of two nights are ±0.057, ±0.040, and ±0.037. 
(2) The agreement of my measures with the Potsdam catalogue. —The mean 
residuals for the different fields range from 0.03 to 0.11, averaging 0.07 (the maxi¬ 
mum residual for a single star is 0.24). This is just about the residual which would 
be expected if the two sets of measures were of equal precision, as the residual 
0.07 is the combined accidental error of the two sets of measures. 
(3) The agreement of my measures with the Harvard values. —The residuals 
range from 0.05 to 0.28, with an average value of ±0.15. If a color correction 
were applied this would be reduced to 0.14, but would still be double the residual 
from the Potsdam catalogue. It is realized that great caution should be used 
in drawing general conclusions from the measures of so few stars; nevertheless, 
the fact that the residuals from the Potsdam system are persistently (except 
for S Lyrae) smaller than from the Harvard system seems to admit of but one 
explanation, the greater accuracy of the Potsdam measures, and the close 
approach to the Potsdam accuracy in the measures of the present series. The 
basing of the Harvard measures on polar stars would naturally introduce greater 
local errors than would be the case in the Potsdam measures, which are based 
on standards near the measured fields. This doubtless accounts for part of the 
difference. 
Table 117.—Standard Magnitude Stars. Agreement of Magnitude Results. 
Field. 
Residuals between my meas¬ 
ures and the catalogue 
magnitudes. 
My measures 
inter se. 
Potsdam Colors. 
Harvard. 
Potsdam. 
Mean. 
No. 
nights. 
Mean 
J. 
1 
2 
3 
4 
1 
2 
34 
H. 
P. 
103 
T Andromedae.. . 
16 
19 
19 
7 
10 
10 . . 
18 
9 
3 
3 
GW- 
w- 
WG- 
267 
V Andromedae.. . 
9 
13 
8 
2 
4 
2 .. 
10 
3 
3 
2 
W- 
w- 
W 
787 
W Andromedae.. . 
6 
2 
17 
, . 
8 
10 
7 • • 
8 
8 
3 
6 
GW- 
GW- 
GW 
431 S 
R Comae. 
14 
2 
11 
10 
12 
2 .. 
9 
8 
3 
6 
WG 
GW 
G- 
5798 RU Herculis. 
13 
7 
11 
3 
3 
8*. . 
10 
5 
3 
4 
GW- 
GW- 
GW- 
6100 
RV Herculis. 
14 
16 
H 
1 
5 
3 • • 
15 
3 
3 
3 
W 
WG 
WG- 
6894 
S Lyrae. 
4 
8 
3 
5 
9 
8 . . 
5 
7 
3 
3 
GW 
GW 
W 
7220 
S Cygni. 
29 
18 
21 
18 
6 
10 . . 
23 
11 
3 
7 
W- 
GW- 
W 
7269 
SX Cygni. 
12 
16 
12 
9 
i 5 
3 • • 
13 
9 
3 
5 
W 
GW 
W 
7458 
V Delphini. 
27 
22 
21 
7 
13 
11}. . 
23 
10 
3 
3 
GW 
WG 
WG 
8518 
Z Cassiopeiae .. . 
32 
26 
32 
20 
12 
6 
ill 1 
28 
10 
4 
4 
WG 
G— 
8629 
Y Cassiopeiae.... 
8 
15 
16 
6 
6 
6 .. 
13 
6 
3 
5 
G— 
WG 
G 
Means. 
15 
7 
4 
Precision of Measures with the Different Apertures. 
The average residual, expressed in hundredths, of the magnitudes of the 
measured stars (not including the standards) from the mean of all the nights, 
is given in the following table for the different apertures separately: 
