Measurement of Atmospheric Extinction Coefficient at Thai National Observatory (TNO)
Abstract
The apparent intensity and color of starlight can be dwindled by the scattering and absorption of the earth's atmosphere. This is called atmospheric extinction, which depends on atmospheric conditions of the observing site and altitude of the targets. This research aims to study the extinction of starlight at the Thai National Observatory (TNO), with an elevation of 2,457 meters, latitude 18.57 ̊N and longitude 98.48 ̊E during a clear sky condition in November 2018. The atmospheric extinction coefficient was investigated using a reflecting telescope with a diameter of 2.4 meters, whose images were captured by a CCD camera through light filters and photometric analysis was carried out using the IRIS software package. The results showed that the atmospheric extinction coefficients were 0.57 ± 0.023 0.33 ± 0.025 0.20 ± 0.013 0.12 ± 0.013 and 0.11 ± 0.065 (magnitudes/airmass) through the wavelength filters of U, B, V, R and I, respectively. There are comparable to the atmospheric extinctions previously reported from observatories in other countries. The atmospheric extinction coefficients were also decomposed into ozone absorption, Rayleigh scattering and Mie scattering components. Ozone absorption affects primarily to the visible wavelength Rayleigh scattering dominates the ultraviolet bands but the extinction decreases rapidly as the wavelength increases. The relation of extinction due to Mie scattering from atmospheric aerosols as a function of wavelength was determined empirically and is given by . This method can be useful in determining aerosol optical properties on a routine basis especially during the nighttime when standard measurement techniques are not viable. The atmospheric extinction coefficient can be used as preliminary compensation data for the TNO. KEYWORDS : the Atmospheric Extinction Coefficients ; apparent magnitude ; airmass ; aerosols ; Rayleigh scatteringReferences
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Chakraborty, P., Das, H.K., & Tandon, S.N. (2005). Exposure Time Calculator for IFOSC and Sky Background Estimation. Bulletin of the Astronomical Society of India, 33 (4), 513.
Dhillon, V.S., Marsh T.R., Atkinson, D.C., Bezawada, N., Bours, M.C.P., Copperwheat, C.M., Gamble, T., Hardy, L.K., Hickman, R.D.H., Irawati, P., Ives D.J., Kerry, P., Leckngam, A., Littlefair, S.P., McLay, S. A., O’Brien, K., Peacocke, P.T., Poshyachinda, S., Richichi, A., Soonthornthum, B. & Vick, A. (2014). ULTRASPEC: a High - Speed Imaging Photometer on the 2.4 m Thai National Telescope, Monthly Notices of the Royal Astronomical Society, 444, 3504–3516, doi:10.1093/mnras/stu1660
Giclas, H.L., Burnham, J.R., & Thomas, N.G. (1971). Lowell Proper Motion Survey Northern Hemisphere. Flagstaff, Arizona: Lowell Observatory.
Gorshelev, V., Serdyuchenko, A., Weber M., Chehade W., & Burrows J. P. (2014). High Spectral Resolution Ozone Absorption Cross-Sections–Part 1: Measurements, Data Analysis and Comparison with Previous Measurements Around 293 K. Atmos. Meas. Tech., 7, 609–624, doi:10.5194/amt-7-609-2014
Hale, S.J., Chaplin, W.J., Davies, G.R., Elsworth, Y.P., Howe, R., Lund, M.N., Moxon, E.Z., Thomas, A., Pallé, P.L., & Rhodes, Jr. E.J. (2017). Atmospheric Extinction Coefficients in the Ic Band for Several Major International Observatories: Results from the BiSON Telescopes, 1984–2016. The Astronomical Journal, 154 (3), 89, doi.org/10.3847/1538-3881/aa81d0
Hu, B. (2011). Preliminary Results of Atmospheric Extinction Coefficient Measurements at Gaomeigu Observational Station. Chinese Astronomy and Astrophysics, 35, 199-208.
Laken, B. A., Parviainen, H., Alejandro, G. - G., Casiana, M. - T., Varela, A. M., Sergio, F. - A., & Pallé, P. (2015). Thirty Years of Atmospheric Extinction from Telescopes of the North Atlantic Canary Archipelag. Journal of Climate, 29(1), doi: 10.1175/JCLI-D-14-00600.1
Landolt, A. U. (1992). UBVRI Photometric Standard Stars in the Magnitude Range 11.5<V<16.0 Around the Celestial Equator. Astronomical Journal, 104 (1), 340-491.
Landolt, A. U., & Uomoto, A. K. (2007). Optical Multicolor Photometry of Spectrophotometric Standard Stars. The Astronomical Journal, 133(3), 768.
Mauna Kea. (2005). Mauna Kea Summit Extinction Values. Retrieved July 1, 2021, from https://www2.keck. hawaii. edu/inst/common/exts.html
Mohan, V., Uddin, W., Sagar, R., & Gupta, S. K. (1999). Atmospheric Extinction at Devasthal, Naini Tal. Bulletin of the Astronomical Society of India, 27, 601-608.
Sanchez-Bajo, F., and Alvarez, D.R.-E. (2012). On the Estimation of Atmospheric Aerosol Extinction Parameters from Measurements in the Johnson–Cousins Photometric System. The Astronomical Society of Australia, 29 (1), 12–19, doi.org/10.1071/AS11037
skinakas observatory. (2019). Project 2 CCD Photometry. July 1, 2019, from http://skinakas2.physics.uoc.gr /en/ outreach/projects/CCD_Photometry_project2/P2_CCD_PHOTOMETRY.pdf
Stalin, C.S., Hegde, M., Sahu, D.K., Parihar, P.S., Anupama, G.C., Bhatt, B.C., & Prabhu, T.P.P. (2008). Night Sky at the Indian Astronomical Observatory During 2000-2008. Bulletin of the Astronomical Society of India, 36, 111-127.
Zhang, H. - H., Liu, X. - W., Yuan, H. - B., Zhao, H. - B., Yao, J. - S., Zhang, H. - W., & Xiang, M. - S. (2005). Atmospheric Extinction Coefficients and Night Sky Brightness at the Xuyi Observation Station. Research in Astronomy and Astrophysics,13 (4), 490-500.
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2023-05-11
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