It appears that observations with an artificial star
have a greater accuracy than field measurements,
obviously due to more favourable circumstances in
a laboratory. This is of course a great advantage
when the personal error of the observer has to be
determined.
Furthermore we can compare the observations made
in the same way with the artificial star, but respect
ively with a manually operated micrometer and a
motor-driven micrometer. For this purpose we
convert the time error into angle error. A deviation
dt in time influences the azimuth with a deviation
da as follows:
da" sin z 15 cos cos q d/s
in which z is the zenith distance of the star. (The
quantity da sin z in (2) is then the effect along the
horizontal wire from (1) and (2) follows the
variance of the azimuth:
a2 sin2z
v2 a0
where the component with b0, which now is in
dependent of the star's velocity, is usually called
"pointing error". The parameter a0 is then actually
the "time error".
Substituting a0 and b0 from table 1 into formulae
(3) gives the following values for the quantity
oa sin z in case of N 1
velocity: 15cos<5cos# 15"/sec 10"/sec 5"/sec
artificial star/manually
operated micrometer: 0."98 0."92 0."88
artificial star/motor-
micrometer: 0."84 0."67 0."60
From this it can be concluded that the standard
deviation of observations made with the motor-
micrometer is approximately 25% better than those
made with the manually operated micrometer.
5 Personal error
The corrections for the observer's personal error
determined using an artificial star are plotted in
Fig. 5 and 6 as a function of the quantity seed sec q.
Each point represents the mean value of two
transits observed immediately after each other in
opposite direction. In this way the influence of an
eventually small displacement of the line of sight
during the measurement is practically eliminated.
The mean correction for the personal error is
determined by a regression line:
observer A: ATp 0/028-0/011 sec5secq
observer B: ATp 0/024 - 0/019 sec c5 sec <7
converting these time errors into angle errors
according to (2) gives:
observer A: Aasinz -0."16 0."42cos<5cosg
observer B: Aasinz -0."28 0."36cos<5cos<7
From (5) we obtain the following values for some
velocities:
15"/sec 10"/sec 5"/sec
observer A: +0."26 +0."12 -0."03
observer B: +0."08 0."05 0." 17
The computation is also carried out with the average
personal error approximated by a better fitting
parabola, as shown in Fig. 5 and 6. Converting the
time errors into angle errors gives:
15"/sec 10"/sec 5"/sec
observer A: +0."05 +0."17 -0."06
observer B: 0."03 0."00 0." 17
Table
number of
measurement instrument contacts transits a„
b0
Laplace
point
Ubachsberg-
Tongeren
(1968)
Laplace
points
Axel,
Rijswijk
(1970)
Artificial
star
(1970)
Artificial
star
(1972)
Wild T4 27
manually
operated
micrometer
DKM 3A
manually
operated
micrometer
DKM 3A
manually
operated
micrometer
DKM 3A
motor-
micrometer
34
32
24
272
176
244
150
0/051 4.'
0/050 4/3
0/030 2/
0/035 1/7
(2)
225 b
N
cos
2 <5 cos21
(3)
(4)
.(5)
52
ngt 73
