ALTAZIMUTH SOLAR OBSERVATIONS, ah 
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C, = ccos* 6 +3 = sin® 20, for 6= 90° to 180° 
In the following table are given the values (i) of the first term 
of the contraction of inclined semidiameters, on the assumption 
that the apparent horizontal semidiameter, that is as reduced by 
refraction, is 16’, and that the difference between the horizontal 
and vertical contractions is 20”: and (ii) also the values of the 
corrected second term which is always to be added, the upper 
number denoting this second correction for the upper, and the 
lower number the second correction for the lower limb of the sun. 
For any other value of the difference of the horizontal, and vertical 
contractions, multiply the first term by the ratio of contraction to 
20”, i.e. by c/20”, and the second term by the square of that ratio 
and add the results. For a different value of the contracted 
horizontal semidiameter, multiply the quantity so found from the 
table, by the ratio of the reduced horizontal semidiameter to 16’. 
The corrections to the tabular values can generally be applied by 
mere inspection. 
= ccos? 0 + 3 © sin? 26, for 8 = 0° to 90° 
1 ...(34) 
is] 
Taste VIII.—Contractions of inclined semidiameters of the 
Sun. the contracted horizontal eetanks being 16’, and vertical 
Sic wcncgacetl 15’ 40". 
a Contraction. vith Contraction. cr, Emer 
0 20:004+-00 30 15-:004+:19 60 5:00+°19 
80 05 0 
1 00 150 05 12 “05 
6 1985 O01 35 13-42.:23 65 857 ‘15 
1 00 145 = 06-118 04 
10 19-40 03 40 11:74 -25 70 234 °1l 
170 oi HS 06 110 03 
15 1866 06 45 1000 :26 75 1:34 -06 
165 02 135 07 105 02 
20 17-66 -11 50 826 -26 80 060 -03 
160 03 130 06 100 01 
