91)
9e)
93)
(94)
le
6)
From (96) it follows that, for target points situated outside the effective
atmosphere, refraction can be expressed in terms of astronomical refraction
denoted by A oo According to [8] we have
^ = tan a + Q tan” 2" to tan? P. tan! ; * ; x
eo? 0, 2 3 = +0 ten z +... (97)
* 4
with etn 22 = v, ctn (2), and for air V 8.1578 3 | SE
: a
The coefficients RRR depend upon the structure of the atmosphere. As
outlined in [11] for precision work it will be necessary to compute n, with the
t A
Cauchy equation as function of the effective wave length and obtain an index. of
refraction profile from Rawinsonde observations. It is then possible with
formula (94) to determine for various (z) values the corresponding C-values by
numerical integration. The corresponding A pp Values, computed from the re-
lation C, - (z) + A oo (Fig. 12) are now used to compute the specific q-
coefficients by fitting the expansion as given by (97) to the computed A co
values.
In order to apply formulas (9h) or (96) to the case of an aerial Observer,
it is necessary to establish the relation between (2), and (z), which is
obtained from (93).
nr sin (z)
sin (z), =—— = —P-P — (98)
nr nr
a a Ta à
The true zenith distances 2 and A are computed, according to Fig. 12 from
sin C
SD
tan 2, = (99)
a
cos Cs =
P
and
-sin C
tan z = + (100)
cos C - -P
65
