Abstract - The paper deals with long-term measuring instruments
for light data collected under the night sky. The point of such
measurements is to quantify the obtrusive light and compare the
level of the obtrusive light in populated industrial areas and out
of them. For long-term measurements of low level illuminances
(about 10-2 lx) and luminances (about 10-3 cd/m2) should be
applied not only the measuring instruments with high sensitivity,
but also completely independent instruments with the ability to
save the measured data.