The Effect of the Installation Angle of the Sky Quality Meter on the Night Sky Brightness and the Beginning of the Fajr Prayer Time
Keywords:Fajr prayer time, Light pollution, Night sky brightness, Sky Quality Meter
AbstractMeasuring the brightness of the night sky and determining the start of Fajr prayer times can be done using SQM. Observations were made at OIF UMSU with coordinates 3o 34' 55.06" N and 98o 43' 17.09" E. The sky brightness was measured using three SQMs mounted facing the zenith, eastern horizon, and western horizon. The night sky brightness values for SQM directed to the zenith, eastern horizon, and western horizon are 18.23 mpsas, 15.82 mpsas, and 15.47 mpsas. The beginning of fajr prayer time produced by SQM is after the beginning of fajr prayer time obtained using the Accurate Times concerning the Sun's altitude 18o below the horizon. The difference obtained by SQM directed to the zenith, eastern horizon, and western horizon is 29.5 minutes, 36.7 minutes, and 39.5 minutes. In other words, the beginning of Fajr prayer time used in Indonesia is earlier than it should be.
 S. Hideaki, â€œResearch on Light Pollution by Using a Sky Quality Meter,â€ Young Sci. J., vol. 6, no. 13, pp. 23â€“24, 2013.
 L. Nurfarida, P. M. Yusup, and N. Komariah, â€œTingkat Pengetahuan Masyarakat Sekitar Observatorium Bosscha Lembang mengenai Polusi Cahaya,â€ J. Kaji. Inf. dan Perpust., vol. 5, no. 1, pp. 13â€“22, Sep. 2017.
 A. Z. Kotarba, S. Chacewicz, and E. Å»mudzka, â€œNight Sky Photometry Over Warsaw (Poland) Evaluated Simultaneously with Surface-Based and Satellite-Based Cloud Observations,â€ J. Quant. Spectrosc. Radiat. Transf., vol. 235, pp. 95â€“107, Sep. 2019.
 S. BarÃ¡, â€œAnthropogenic Disruption of the Night Sky Darkness in Urban and Rural Areas,â€ R. Soc. Open Sci., vol. 3, no. 10, pp. 1â€“14, Oct. 2016.
 P. Cinzano, â€œNight Sky Photometry with Sky Quality Meter,â€ ISTIL Internal Report. pp. 1â€“14, 2005.
 N. F. Ngadiman, N. N. M. Shariff, and Z. S. Hamidi, â€œSensor Technology for Night Sky Brightness Measurements in Malaysia,â€ Int. J. Recent Technol. Eng., vol. 8, no. 6, pp. 198â€“202, Mar. 2020.
 Y. Pramudya and M. Arkanuddin, â€œThe Sky Brightness Measurement during the 2016 Solar Eclipse in Ternate,â€ J. Phys. Conf. Ser., vol. 771, no. 1, pp. 2â€“6, Nov. 2016.
 F. F. R. S. Hamdani and L. A. H. Noor, â€œThe Dawn Sky Brightness Observations in the Preliminary Shubuh Prayer Time Determination,â€ QIJIS (Qudus Int. J. Islam. Stud., vol. 6, no. 1, pp. 25â€“37, Jul. 2018.
 A. Bertolo, R. Binotto, S. Ortolani, and S. Sapienza, â€œMeasurements of Night Sky Brightness in the Veneto Region of Italy: Sky Quality Meter Network Results and Differential Photometry by Digital Single Lens Reflex,â€ J. Imaging, vol. 5, no. 56, pp. 1â€“13, May 2019.
 A. HÃ¤nel et al., â€œMeasuring Night Sky Brightness: Methods and Challenges,â€ J. Quant. Spectrosc. Radiat. Transf., vol. 205, pp. 278â€“290, Jan. 2018.
 J. Zamorano et al., â€œTesting Sky Brightness Models Against Radial Dependency: A Dense Two Dimensional Survey Around the City of Madrid, Spain,â€ J. Quant. Spectrosc. Radiat. Transf., vol. 181, pp. 52â€“66, Sep. 2016.
 A. Y. Raisal, Y. Pramudya, O. Okimustava, and M. Muchlas, â€œPemanfaatan Metode Moving Average dalam Menentukan Awal Waktu Salat Subuh Menggunakan Sky Quality Meter (SQM),â€ Al-Marshad J. Astron. Islam dan Ilmu-Ilmu Berkaitan, vol. 5, no. 1, pp. 1â€“13, 2019.
 S. A. M. Nor and M. Z. Zainuddin, â€œSky Brightness for Determination of Fajr and Isha Prayer by Using Sky Quality Meter,â€ Int. J. Sci. Eng. Res, vol. 3, no. 8, pp. 132â€“134, 2012.
 A. Y. Raisal, Y. Pramudya, O. Okimustava, and M. Muchlas, â€œThe moon phases influence on the beginning of astronomical dawn determination in Yogyakarta,â€ Int. J. Sci. Appl. Sci. Conf. Ser., vol. 2, no. 1, p. 1, 2017.
 I. Plauchu-Frayn et al., â€œNight sky brightness at San Pedro Martir observatory,â€ Publ. Astron. Soc. Pacific, vol. 129, no. 973, pp. 1â€“13, 2017.
Authors who publish in IRiP agree to the following terms: Authors retain copyright and grant the IRiP right of first publication with the work simultaneously licensed under a Creative Commons Attribution License (CC BY-SA 4.0) that allows others to share (copy and redistribute the material in any medium or format) and adapt (remix, transform, and build upon the material) the work for any purpose, even commercially with an acknowledgment of the work's authorship and initial publication in IRiP. Authors are able to enter into separate, additional contractual arrangements for the non-exclusive distribution of the journal's published version of the work (e.g., post it to an institutional repository or publish it in a book), with an acknowledgment of its initial publication in IRiP. Authors are permitted and encouraged to post their work online (e.g., in institutional repositories or on their website) prior to and during the submission process, as it can lead to productive exchanges, as well as earlier and greater citation of published work (See The Effect of Open Access).