r- r 
CHAPTER XIV.—GENERAL CONCLUSIONS. 
189 
Table 118.—Magnitude Residuals eor Measured Stars. 
Aperture. 
6 
12 
40 
Mean. 
103 
T Andromedse.. . 
9 
9 
11 
10 
267 
V Andromedae... 
8 
10 
7 
8 
787 
W Andromedse... 
7 
4 
6 
6 
4315 
R Comse. 
8 
6 
11 
8 
5798 RU Herculis. 
8 
7 
13 
9 
6100 
RV Herculis. 
5 
6 
15 
9 
6894 
S Lyrae. 
4 
6 
12 
7 
7220 
S Cygni. 
4 
8 
18 
10 
7269 
SX Cygni. 
7 
5 
12 
8 
7458 
V Delpliini. 
7 
6 
9 
7 
8518 
Z Cassiopeia ... 
8 
7 
5 
7 
8629 
Y Cassiopeiae .. . 
6 
5 
14 
8 
Mean. 
7 
7 
11 
8 
II. LIMIT OF VISION OF THE 6-, I 2-, AND 40-INCH TELESCOPES. 
An interesting result of the present investigation is the photometric magni¬ 
tude of the limit of vision of the three telescopes used. The estimates of the limit 
are given for each field in the table “Visual Comparisons of the Variable” in 
steps below the faintest comparison star visible. Table 119 collects the most reli¬ 
able of these estimates, made in good seeing and classified for each aperture accord¬ 
ing to the ocular used, as it is well known that a higher magnifying power will 
show fainter stars. Following the columns giving the field, date of observation, 
and estimate of limit, are two magnitude columns on the H. C. O. system, giving 
the photometric magnitude of the star used in the estimate and the resulting 
apparent magnitude of the limit, using as the value of one step 0.14. The next 
two columns give the zenith distance and the reduction to the zenith resulting 
from atmospheric absorption. The final two columns give the zenith magnitude 
of the limit, both in the Harvard and Potsdam systems. Using Pogson’s formula 
Limit of vision = 9.0+5 log aperture in inches 
we have the following comparison between calculated and observed limits:* 
6-inch, calculated. 
6-inch, observed, ocular 150. 
6-inch, observed, ocular 150. 
12-inch, calculated. 
12-inch, observed, ocular 275 
12-inch, observed, ocular 275 
40-inch, calculated. 
40-inch, observed, ocular 750 
40-inch, observed, ocular 750 
12.89. 
12.90 Harvard scale. 
13.02 Potsdam scale. 
14.40. 
14.27 Harvard scale. 
14.57 Potsdam scale. 
17.01. 
16.8 Harvard scale. 
17.1 Potsdam scale. 
* Compare provisional results from six fields in Table 4, page 10. 
