 |
 |
 |
 |
 |
 |
Sains Malaysiana 47(11)(2018): 2877–2885 http://dx.doi.org/10.17576/jsm-2018-4711-31
Measuring the Sun Depression Angle
of Dawn with a DSLR Camera (Mengukur Sudut Junaman Matahari bagi Fajar
menggunakan Kamera DSLR) KASSIM BAHALI1*,
ABDUL
LATIF
SAMIAN1,
NAZRI
MUSLIM2
& NURUL SHAZANA ABDUL
HAMID3 1Institute of the Malay World &
Civilization (ATMA), Universiti Kebangsaan Malaysia, 43600 UKM
Bangi, Selangor Darul Ehsan, Malaysia 2Pusat Citra Universiti, Universiti
Kebangsaan Malaysia, 43600 UKM Bangi, Selangor Darul Ehsan, Malaysia 3School of Applied Physics, Faculty
Science and Technology, Universiti Kebangsaan Malaysia, 43600
UKM Bangi, Selangor Darul Ehsan, Malaysia Received: 15 May 2018/Accepted:
27 July 2018 ABSTRACT The first visibility of the
dawn occurs at a definite angle of the sun depression, Do which
is used to calculate the fajr (dawn) prayer time. Dawn observations
were carried out using Digital Single-lens Reflex (DSLR)
camera in the period from February to December 2017 at several
locations in both Malaysia and Indonesia (Lat. between 2.0° -
7.0° N, Long. 95.0°-106.0°E). Within the observational period,
64 days of the dawn luminance at horizon were recorded with backgrounds
of both sea and land. The purpose of these observations was to
determine the sun depression angle Do at
the first moment when the dawn is seen using a DSLR camera.
The results indicated that Do can be determined using a DSLR
camera. The value of Do is between -14.5° and -18.5°
with a mean value of -16.67° and standard deviation of 0.9992.
This suggests that the new sun depression angle Do for dawn prayer is -17.0°. Keywords: Dawn; digital camera;
sun depression angle ABSTRAK Fajar mula-mula kelihatan berlaku
pada suatu sudut junaman matahari Do yang
tertentu yang digunakan untuk menghitung waktu solat subuh. Pencerapan
fajar telah dilakukan menggunakan kamera digital kanta pemantul
tunggal (DSLR)
dalam tempoh dari Februari hingga Disember 2017 di beberapa lokasi
di Malaysia dan Indonesia (Lat. di antara 2.0° - 7.0° U, Long.
95.0°-106.0°T). Dalam tempoh tersebut, 64 data cerapan kecerahan
fajar di ufuk laut dan daratan telah direkodkan. Tujuan pencerapan
ini adalah untuk menentukan sudut junaman matahari Do ketika fajar mula-mula kelihatan dengan kamera DSLR.
Keputusan kajian menunjukkan Do boleh ditentukan dengan kamera
DSLR dan nilai Do di antara -14.5° hingga -18.5°
dengan min -16.67° dan sisihan piawai 0.9992. Dengan hal demikian,
dicadangkan nilai sudut junaman baharu Do bagi solat subuh ialah -17.0°. Kata kunci: Fajar; kamera digital; sudut junaman matahari REFERENCES Baharrudin
Zainal. 2002. Pengenalan Ilmu Falak. Dewan Bahasa dan Pustaka.
Kuala Lumpur. Berry,
R. & Burnell, J. 2005. The Handbook of Astronomical Image
Processing. 2nd ed. Richmond,VA: Willmann-Bell, Inc. Chris,
W. 2018. The Science of Candle. http://www. explainthatstuff.com/candles.html.
Accessed on 22 July 2018. Dhani Herdiwijaya. 2016. Sky brightness and twilight
measurements at Jogyakarta city, Indonesia. Journal of Physics:
Conference Series 771: 012033. https://doi. org/10.1088/1742-6596/771/1/012033.
Duriscoe, M. 2016. Photometric
indicators of visual night sky quality derived from all-sky brightness
maps. Journal of Quantitative Spectroscopy and Radiative
Transfer 181: 33-45. Hanel, A., Posch, T., Ribas,
S.J., Aubée, M., Duriscoe, D., Jechow, A., Kollath, Z., Lolkema,
D.E., Moore, C., Schmidt, N., Spoelstra, H., Wuchterl, G. &
Kyba, C.C.M. 2018. Measuring night sky brightness: Methods and
challenges. Journal of Quantitative Spectroscopy and Radiative Transfer 205: 278-290.
Hassan,
A.H. & Yasser A. Abdel Hadi. 2014. Naked eye determination
of the dawn at Tubruq of Libya through four years observation.
Middle-East Journal of Scientific Research 23(11): 2627-2632. Hassan,
A.H. & Issa, I.A., Mousa, M. & Yaser, A. Abdel-Hadi. 2016.
Naked eye determination of the dawn for Sinai and Assiut of Egypt.
NRIAG Journal of Astronomy and Geophysics 5(1): 9-15. Hiscocks,
P. 2014. Measuring Luminance with a Digital Camera. Syscomp
Electronic Design Limited. www.syscompdesign.com. Ilyas, M. 1984. A
Moder Guide to Astronomical Calculation of Islamic Calendar,
Times & Qibla. Kuala Lumpur: Berita Pub. Sdn Bhd Issa, I.A. & Hassan, A.H. 2008.
Eye criteria and times of end and begin of twilights Bahria Egypt
NRIAG. Journal Astron. Astrophysis (Special Issue): 413-423.
Kishida, Y. 1989. Changes in light
intensity at twilight and estimation of the biological photoperiod.
Journal of Japanese Agriculture 22: 4. Zhang, M., Bakos, G.A., Penev, K.,
Csubry, Z., Hartman, J.D., Bhatti, W. & de Val-Borro, M. 2016.
Precision multiband photometry with a DSLR camera. Journal
of the Astronomical Society of the Pacific 128: 961. *Corresponding author;
email: kassimhb@gmail.com
|
|||
|
