Problems of Shemakha Observatory in Azerbaycan

From the paper by D.I.Shestopalov et al., 2006, Azerbaycan Astronomiya Jurnali No.1-2, 53

"Since the end of 1990-th up today, the conditions of astronomical observations in the region of the observatory became worse abruptly. They became due to unchecked privatization of the land near the boarders of the national reserved zone and uncontrolled development of the wild tourist bussiness. At the present time, more than 20 restaurants, kempings and rest bases gather round the observatory inside the radius of one kilometer. As a rule, they are located on the tips of nearby hills, so that dosens of luminescent and incandescent lamps fill with the light the observation sight where the telescopes are installed. Furthermore, the intensity of the motion of cars increased sharply during the night with the people who like to relax in the country. Bright flashes of car headlights get inside the domes where the telescopes are installed, and, as minimum, brake up the observations, but, as maximum, threaten to destroy the expensive equipment. One should note additionally that the peak of tourist season falls on the summer period when the quality of observational nights is the best according to results taken in [3]".
"It was found as a result of the reduction of photometrical observations that the night sky background at the minimum heights above the horizon is equal to 18m.6 per squire arcsecond with the corresponding dispersion value of 0m.4, taking into account that the analogous value for the ideally clean sky is equal to 22m-23m".

Light pollution of the night sky in the region of 6-meter telescope BTA of the Special Astrophysical Observatory of the Russian Academy of Sciences.

Goranskij, V.P. (SAI, Moscow University)

Spectrum of the night sky

Taking into account increasing light interference in the astronomical observations in SAO, I have carried out the investigation of composition of night airglow and its time variations, and tried to establish the cause of this interference. 104 long-slit spectra available for me were used as a basic matherial for investigation. The spectra were taken with UAGS and SCORPIO spectrographs at BTA, and also with UAGS spectrograph at 1-m Zeiss reflector, located near BTA. Spectral resolution was 1.4-5.0 A with BTA/UAGS, 13A using grism VPHG550G, and 4.6 A using VPHG1200G with BTA/SCORPIO. Spectral resolution with Zeiss/UAGS was 2.2 - 10.1 A.

Typical spectra taken with SCORPIO are shown in the Fig. 1 and 2.

Fig. 1. The spectrum of SAO night sky airglow in the blue range taken with BTA and SCORPIO spectrograph with the VPHG1200G grizm at the moonless night on 2008 February 6.

Fig. 2. The spectrum of SAO night sky airglow in the red range taken with BTA and SCORPIO spectrograph with the VPHG550G grizm at night on 2007 November 17 with the declining moon at the phase of 0.7.

The emission lines in the sky spectrum are identified according to paper by V.V.Vlasyuk and O.I.Spiridonova (Russian Astron. Zhurnal V.70, 773, 1993). In the blue region, there are many absorption lines of solar spectrum. Probably, this is the light of the Sun scattered on the interplanetary dust. The emissions of H, [NI] 5198 and 5200 A, [OI] 5577, 6300 and 6364 A, molecular bands of O2, and Meinel bands of OH molecule have natural origin, and are forming in the upper layers of the Earth atmosphere at the altitudes of 90-300 km (C.R.Benn and S.L.Ellison, La Palma Night-Sky Brightness). In the cited paper, the results of such a kind of investigation are given for the sky lines and their variations at La Palma island. HgI lines have artificial origin, they originate from the street lighting with the glow-discharge lamps, and distinguish oneself with the white light. Mercury radiates in the visible range at the wavelengths of 4046, 4358, 5460, 5769 and 5790 A. Sodium emission NaI D2D1 5890 and 5896 A has both the natural and artificial components. Probably, natural sodium gets the upper layers of the atmosphere due to wind transfer of oceanic salt. The artificial component originates from the street lighting by glow-discharge low- pressure sodium lamps, these sources differ by orange glow.

Our night sky spectra were taken usind different telescopes, devices, grisms, gratings and slits, so, the absolute calibration of line intensities in these spectra is impossible. Therefore, the intensity ratios were determined for the lines of artificial origion to the lines of natural origion. Natural [OI] 5577 A emission was chosen as a reference line. It is known that the strength of this emission varies with the solar cycle, it is known that the minimum of solar cycle occured in 2007 (see Benn and Ellison). The central intensities of this line were measured, along with central intensities of nearby lines of HgI 5460 A and NaI 5890/5896 A. Of course, the intensity of background continuum was deleted.

Observations were performed at different weather conditions: both, at clear sky, and through cirri and small clouds. In the spectra taken through the clouds, the intensity of [O I] decreases due to absorption by clouds, but the intensity of artifitial emissions of HgI and NaI vice versa increases due to light scattering on the clouds. So, the values of intensity ratios of studied lines to [O I] should increase when the weather conditions become worse.

Observations of intensity ratios HgI and NaI to [O I].
Characteristics of interference due to light pollution at the SAO observational sight.
Light pollution sources-1.
Light pollution sources-2.
Results and conclusions.
Continued. Monitoring the situation.