Development of measuring instruments for long-term measurement of low level illuminances and luminances

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. For low level illuminances measuring is described luxmeter satisfying the above requirements. The issue of measuring the low luminances is solved by digital photographs. In this paper is also showed the astronomical camera with cooled CCD chip, which is able to minimize the thermal noise. The last described device for long-term measuring of the night sky is astronomical instrument (Sky quality meter), which evaluates the luminances of the night sky. This instrument does not work with lighting units (cd/m²), but in magnitudes (mag). For traditional reasons, astronomers use the term magnitude, expressed in units called magnitudes. Magnitude is a logarithmic value. This instrument is able to compare the astronomical measurements and lighting ones. For illuminances measurement is needed photovoltaic sensor capable to convert low illuminances to electricity. Nowadays luminance measurements with the digital photography is very effective in levels from 1 cd/m² to 100 000 cd/m². However, for measuring of very low level luminances it is not enough and there must be used very sensitive CCD cameras with cooled chips.