16 
RESEARCHES IN STEECAR PHOTOMETRY. 
Table 8.—103 T Andromeda—C ontinued. 
1905 February 25. 
Fair to good, low. 
Sidereal 
Zen. 
Mean Scale Readings. 
Magnitude. 
Star. 
Scale Readings. 
C. 
Time. 
Dist. 
Mean of 3 
Mean of 6. 
H. 
P. 
h m 
O 
t 
22.2 22.1 22.3 
22.20 
21.68 
1.89 
11.89 
11.97 
k 
21.3 22.4 22.7 
22.13 
20.46 
i -75 
11 75 
11.83 
z 
41.5 42.3 42.9 
42.23 
42.82 
4.08 
14.08 
14.16 
TV 
4°-3 39-3 4 °- 2 
39-93 
40.05 
3 - 79 
13-79 
13-87 
Va, 
11.5 10.4 11.4 
11.10 
10.82 
0-53 
10.53 
10.6r 
y 
48.2 48.1 48.9 
48.40 
47-76 
4.60 
14.60 
14.68 
X 
3 2 •5 33-8 32 -9 
33-07 
33-25 
3.00 
13.00 
1308 
u 
35.2 35.1 34.7 
35-00 
34.68 
3.16 
13.16 
13-24 
u 
34.4 34.0 34.7 
34-37 
. 
X 
32.8 34.2 33.3 
33 • 43 
y 
46.9 47.3 47.2 
47 - 13 
T>ai 
10.2 10.3 11.1 
10.53 
w 
40.6 39.8 40.1 
40.17 
z 
42.5 44.5 43.2 
43 • 40 
k 
18.2 21.3 19.9 
19.80 
. „ . . 
35 
t 
20.0 21.7 218 
21.17 
Table 8 gives the detailed photometric measures and reductions of the com¬ 
parison stars in Table 7, based on the stars in Table 5. The series measured on 
three nights with the 6-inch includes the three catalogue stars A, B, and a, also 
the six comparison stars, b, c, d, e, l, and s. A complete series consists of three 
settings on each star in the list, followed immediately by three more settings on 
the stars in reverse order. Thus the mean of the times is the same for each star 
and any progressive changes in the real or the artificial star will be eliminated. 
In the seventh column there are two mean scale readings for each star, which 
are united into the single mean of the eighth column. The ninth column contains 
the values of C (curve reading) corresponding to each mean scale reading. These 
are taken from the absorption curves, E 6 for the 6-inch and A 12 for the 12- 
and 40-inch, and express the relative magnitudes of the stars as explained 
below. To convert C into magnitudes in the system of the catalogue, it is 
increased by the quantity M 0 taken from Table 9. For example, on October 15 
the mean C for the three standard stars is 0.88; the mean of their magnitudes 
from the H. C. O. Catalogue is 7.69; the difference in the two quantities, called 
M 0 , is 6.81. If M° be added to each C, the mean of the sums for the three stand¬ 
ard stars will agree with the mean of their catalogue magnitudes, and the separate 
sums will preserve the relative magnitudes as measured. The quantity M 0 is 
the magnitude of the zero reading on the absorption curve, and when increased 
by the C of each star will give the magnitude in the system used. In the example 
we are using the M 0 in the Potsdam system is 6.89. Adding these values of M 0 
to C we have the last two columns of Table 8, the measured magnitudes in the 
H. C. O. and P. DM. systems. 
The sidereal time and zenith distance, given in the first two columns of Table 8, 
serve to show that no correction is needed for change in atmospheric absorption 
due to difference in zenith distance between the standard stars and the stars to 
be measured. For example, on October 15, when the field was near the meridian, 
