|
|
Aubé, M., Fortin, N., Turcotte, S., García, B., Mancilla, A., & Maya, J. (2014). Evaluation of the Sky Brightness at Two Argentinian Astronomical Sites. Publications of the Astronomical Society of the Pacific, , 000.
Abstract: Light pollution is a growing concern at many levels, especially for the astronomical community. Indeed, not only does artificial lighting veil celestial objects, it disturbs the measurement of many atmospheric phenomena. The sky brightness is one of the most relevant parameters for astronomical site selection. Our goal is to evaluate the sky brightness of two Argentinian observation sites: LEO ++ and El Leoncito. Both sites were preselected to host the Cherenkov Telescope Array. This project consists of an arrangement of many telescopes that can measure high-energy gamma ray emissions via their Cherenkov radiation produced when entering the earth’s atmosphere. In this paper, we describe the measurement methods used to determine whether those sites are valuable or not. We compared our results with the sky radiance of different renowned astronomical sites (Kitt Peak, Arizona, and Mont-Mégantic, Québec, Canada). Among our results, we found that LEO ++ is a good site, however the presence of a low layer of local aerosol can introduce uncertainties in the measurements. Consequently, El Leoncito would be a better option for such an installation. This latter site shows very low sky brightness levels, which are optimal for low light detection.
|
|
|
|
Benn, C. R., & Ellison, S. L. (1998). La Palma night-sky brightness.
Abstract: The brightness of the moonless night sky above La Palma was measured on 427 CCD images taken with the Isaac Newton and Jacobus Kapteyn Telescopes on 63 nights during 1987 – 1996. The median sky brightness at high elevation, high galactic latitude and high ecliptic latitude, at sunspot minimum, is B = 22.7, V = 21.9, R = 21.0, similar to that at other dark sites. The main contributions to sky brightness are airglow and zodiacal light. The sky is brighter at low ecliptic latitude (by 0.4 mag); at solar maximum (by 0.4 mag); and at high airmass (0.25 mag brighter at airmass 1.5). Light pollution (line + continuum) contributes < 0.03 mag in U, approximately 0.02 mag in B, approximately 0.10 mag in V, approximately and 0.10 mag in R at the zenith.
|
|
|
|
Hampf, D., Rowell, G., Wild, N., Sudholz, T., Horns, D., & Tluczykont, M. (2011). Measurement of night sky brightness in southern Australia. Advances in Space Research, 48(6), 1017–1025.
Abstract: Night sky brightness is a major source of noise both for Cherenkov telescopes as well as for wide-angle Cherenkov detectors. Therefore, it is important to know the level of night sky brightness at potential sites for future experiments.
The measurements of night sky brightness presented here were carried out at Fowler’s Gap, a research station in New South Wales, Australia, which is a potential site for the proposed TenTen Cherenkov telescope system and the planned wide-angle Cherenkov detector system HiSCORE.
A portable instrument was developed and measurements of the night sky brightness were taken in February and August 2010. Brightness levels were measured for a range of different sky regions and in various spectral bands.
The night sky brightness in the relevant wavelength regime for photomultipliers was found to be at the same level as measured in similar campaigns at the established Cherenkov telescope sites of Khomas, Namibia, and at La Palma. The brightness of dark regions in the sky is about 2 × 1012 photons/(s sr m2) between 300 nm and 650 nm, and up to four times brighter in bright regions of the sky towards the galactic plane. The brightness in V band is 21.6 magnitudes per arcsec2 in the dark regions. All brightness levels are averaged over the field of view of the instrument of about 1.3 × 10−3 sr.
The spectrum of the night sky brightness was found to be dominated by longer wavelengths, which allows to apply filters to separate the night sky brightness from the blue Cherenkov light. The possible gain in the signal to noise ratio was found to be up to 1.2, assuming an ideal low-pass filter.
|
|
|
|
Massey, P., & Foltz, C. Â. B. (2000). The Spectrum of the Night Sky over Mount Hopkins and Kitt Peak: Changes after a Decade1. Publ Astron Soc Pac, 112(770), 566–573.
Abstract: Recent (1998–1999) absolute spectrophotometry of the night sky over two southern Arizona astronomical sites, Kitt Peak and Mount Hopkins, is compared to similar data obtained in 1988 at each site. The current zenith sky brightness in the range ∼3700–6700 Ã… is essentially identical at the two sites and is as dark now as Palomar Observatory was in the early 1970s, when it was generally considered a premier dark observing site. Converted to broadband measurements, our spectrophotometry is equivalent to , mag arcsec−2, for the zenith night sky. The contribution of high‐pressure sodium street lights to broadband V is about 0.2 mag arcsec−2, comparable to the strong airglow O i λ5577 line. During the period from 1988 to 1998–1999, the zenith sky brightness increased only modestly, with the largest changes being seen for Kitt Peak, where the zenith sky has brightened by ≈0.1–0.2 mag arcsec−2 in the blue‐optical region. For Kitt Peak we also have both 1988 and 1999 observations at modestly large zenith distances ( ). In the directions away from Tucson, the sky has brightened by ≈0.35 mag arcsec−2 over the intervening decade. Toward Tucson the change has been larger, approximately 0.5 mag arcsec−2. In most directions the increase in the sky brightness has lagged behind the fractional increase in population growth, which we attribute to good outdoor lighting ordinances, a fact which is further reflected in the decrease in Hg emission. However, our results emphasize the need for diligent attention as developments creep closer to our observing sites.
|
|
|
|
Noll, S., Kausch, W., Barden, M., Jones, A. M., Szyszka, C., Kimeswenger, S., et al. (2012). An atmospheric radiation model for Cerro Paranal: I. The optical spectral range*. A&A, 543, A92.
Abstract: Aims. The Earth’s atmosphere affects ground-based astronomical observations. Scattering, absorption, and radiation processes deteriorate the signal-to-noise ratio of the data received. For scheduling astronomical observations it is, therefore, important to accurately estimate the wavelength-dependent effect of the Earth’s atmosphere on the observed flux.
Methods. In order to increase the accuracy of the exposure time calculator of the European Southern Observatory’s (ESO) Very Large Telescope (VLT) at Cerro Paranal, an atmospheric model was developed as part of the Austrian ESO In-Kind contribution. It includes all relevant components, such as scattered moonlight, scattered starlight, zodiacal light, atmospheric thermal radiation and absorption, and non-thermal airglow emission. This paper focuses on atmospheric scattering processes that mostly affect the blue (<0.55 μm) wavelength regime, and airglow emission lines and continuum that dominate the red (>0.55 μm) wavelength regime. While the former is mainly investigated by means of radiative transfer models, the intensity and variability of the latter is studied with a sample of 1186 VLT FORS 1 spectra.
Results. For a set of parameters such as the object altitude angle, Moon-object angular distance, ecliptic latitude, bimonthly period, and solar radio flux, our model predicts atmospheric radiation and transmission at a requested resolution. A comparison of our model with the FORS 1 spectra and photometric data for the night-sky brightness from the literature, suggest a model accuracy of about 20%. This is a significant improvement with respect to existing predictive atmospheric models for astronomical exposure time calculators.
|
|
