ASTRONOMICAL OBSERVATIONS. 
547 
Example .—March 11th, 1881, P.M., at place, the following observa¬ 
tions of Venus (W. of meridian) were taken to find A.T. at place, and 
thence the longitude. Index error — 3 in. 10 secs., the error of watch 
on Feb. 22nd, 1881, was 80 secs, fast on Gr.M.T., and its daily rate was 
1 sec. gaining. Lat. 51° 30' 30" 
Longitude by Altitude oe a Star or Planet. 
Latitude, 51° 30' 30" N. 
Date, 1881. Times by watch. 
Alts, of star in artl. horizon. 
h. m. 
sec. 
Month. Day. h. m. sec. 
o / 
" 
*’s R.A. (N.A.) ... 
2 10 47 
March 11th . 7 30 13 
52 16 
10 
7 31 19 
52 32 
20 
7 32 28 
52 48 
30 
o t 
" 
— 
— 
*’s Decln. (N.A.) 
17 17 45 N. 
3 ) 22 34 00 
3 ) 157 37 
00 
90 
Mean . 7 31 20 
Mean . 
. 52 32 
20 
#’ s Polar dist. 
72 42 
15 N. 
Error of watch... — 30 
Index error 
... - 3 
10 
_ 
h. m. 
sec. 
7 30 50 
2 ) 52 29 
10 
Siderial time (p. ii. 
Accumulated rate — 17 
N.A.) Mar. 11 
23 17 
8-81 
26 14 
35 
Acceln. for 7h. = 
0 1 
9 
Month. Day. 
Refraction., 
. - 1 
57 
n 30m. = 
0 4 
4-93 
G.M.T., March 11th 7 30 33 
— 
a 33 secs. = 
: 0 0 
0-09 
26 12 
38 
Parallax in altitude 
Mean sun’s R.A. = 
23 18 
22-83 
(tab. 45 Raper) + 
13 
True alt.... 
. 26 12 
51 
O / // 
*’s true alt. 
. 26 12 51 
Latitude. 
. 51 30 30 
Sec. 
. 0-205930 
Polar dist. 
. 72 42 15 
Cosec. 0-020095 
Sum .... 
2 ) 150 25 36 
£ sum ... 
. 75 12 48 
Cosin. 9-406918 
% sum — 
- alt. = remdr. = 48 59 57 
Sin. 
h. m. 
secs. ■ ~— 
*’s hour Z . 
.... 4 37 
37 = Log. sin. sq 
«. = 9-510710 
*’s R.A. 
.... 2 10 
47 
R.A. of meridian .. 
.... 6 48 
24- 
Mean sun’s R.A. .. 
.... 23 18 
23 
M.T. at place. 
. 7 30 
1 
G.M.T. 
.... 7 30 
33 
Long, in time. 
32 = 0° 8' 
0" longitude, W t 
N.B.—When the star is to the west of the meridian add the hour Z to the star’s R.A .; when 
to the east, subtract the star’s Hour Z from its R.A. (increased if necessary by 24 hours); the 
result is the R. A. of the Meridian. Prom the R.A. of the Meridian (increased if necessary by 
24 hours) substract the R.A. of the Mean Sun, and the result will be the Mean Time at place of 
observation. 
III.— Finding Variation of Compass by Amplitude. 
Example .—On 6th Jan., 1872, at 4 h. 44 m. 27s., A.M., A.T. at place, 
in Latitude 37° 59' S., and Longitude 36° 24' W., the sun’s Magnetic 
Variation of 
compass. 
