28 
RESEARCHES IN STEEEAR PHOTOMETRY. 
Table 14.—Photometric Measures and Color op Comparison Stars. 
H. M. j J. A. Parkhurst. 
Star. 
H. C. 0 . 
37,151 
Lindemann 
+ 0.18 
A. N. 139,345 
a 
8.08 
8.03 
b 
8-45 
8.80 
c 
d 
9.01 
9.29 
e 
l 
s 
10.62 
t 
12.34 
k 
12.50 
X 
13-89 
V 
Parkhurst j 
.rarKiiursL 
A. J.15,77 
H. 
P. 
8.51 
7.98 
8.06 
8.76 
8.72 
8.80 
9-51 
9-59 
9.26 
9.12 
9.20 
10.20 
10.28 
10.15 
10.23 
10.32 
10.40 
11.66 
11.74 
12-55 
11.85 
11 93 
13.12 
13.20 
Yendell, 
Visual 
A. J. 15.93 
Color, 
Plates 
149 and 150 
Hagen 
8.18 
+ 0.37 
8. 1 
8. 10 
— 0.02 
8-5 
9.07 
-0.03 
9.0 
8.58 
+ 0.11 
8.8 
9.60 
— 0.08 
9-7 
10.20 
+ 0.11 
9-9 
+ 0.10 
10.0 
+ 0.08 
12.4 
— 0.09 
12.5 
+ 0.52 
Table 14 collects the other photometric measures of these comparison stars 
which are known to the writer, adding Hagen’s and Yendell’s visual scales and 
the measure of the color from a comparison of photographs taken on ordinary 
and isochromatic plates. The Harvard results in the second column reveal a 
considerable difference in scale, but reference to the volume cited shows that 
the measures of the four faint stars depend on the single star d, which seems too 
narrow a foundation. Again, before any larger aperture had been used on the 
field, the writer selected the comparison star x with the 6-inch reflector, whose 
limit of vision, as determined by all the photometer measures, lies between 12.8 
and 13.0. If this is true the Harvard values for the faint stars are numerically 
too large by at least three-quarters of a magnitude. 
Tindemann’s results were based on the magnitude 6.50 for the star B. D. 
+ 26°23 (P. DM. 6.68) and are therefore increased by 0.18 to bring them to the 
Potsdam system. They show a very close agreement with my values in column P. 
H. M. Parkhurst’s measures make the yellow star a about half a magnitude 
fainter than the other values. The Purkinje phenomenon would seem to explain 
the difference, as he used an extinction photometer, while the others used the 
full light of the star. A difference in scale is also indicated by the single faint 
star k, but this is entitled to a relatively small weight as it depends on only two 
double extinctions, while the other stars have six to nine; and in other fields our 
scales are in good agreement. 
The writer’s results are given in columns H and P on both the Harvard and 
Potsdam scales. 
Yendell’s visual scale is added for comparison. The color of the star a probably 
accounts for his estimating it with a 4.25-inch aperture fainter than the star b. 
The “Color” column gives the difference: Magnitude on ordinary plate minus 
magnitude on isochromatic plate. It will be noticed that these differences are 
within the combined accidental errors of the visual and photographic measures, 
except for the stars a and v. At the present writing the data are insufficient for 
expressing these color numbers on the usual decimal scale, but an idea of their 
