Measuring luminance and sun depression angle of dawn

Research output: Contribution to journalArticle

Abstract

Dawn are difficult to be seen when it first rises due to weather conditions and the low intensity of dawn light along with the factor of low visual acuity of the observer. In that case, the detection of the early emergence of dawn by using photometry is very important. The photometric device can detect and measure the dawn luminance, the moment it starts emerging. This study aims to measure the luminance of dawn, LD and the sun depression angle, D when the dawn began to appear by using a photometer, Sky Quality Meter (SQM) and Digital Single Lens Reflex (DSLR). The result of the measurement using these two tools were compared in terms of the luminance value and the measured value of the sun depression angle. The study was conducted from June to December 2017 in seven locations around Malaysia and Indonesia. The study found that the average value of LD is 19.47 mag arcsec -2 and 20.85 mag arcsec -2 with a DSLR and SQM, respectively. On the other hand, the average value obtained for D is -17.00° and -16.56° with DSLR and SQM, respectively. We therefore propose that LD is between 19.50 mag arcsec -2 and 20.90 mag arcsec -2 while D of the dawn is -17.00°.

Original languageEnglish
Pages (from-to)1136-1150
Number of pages15
JournalInternational Journal of Mechanical Engineering and Technology
Volume10
Issue number2
Publication statusPublished - 1 Feb 2019

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Sun
Luminance
Lenses
Photometry
Photometers

Keywords

  • Instrumentation: Photometer
  • Methods: Observational
  • Techniques: Image processing
  • Techniques: photometric

ASJC Scopus subject areas

  • Mechanics of Materials
  • Mechanical Engineering
  • Industrial and Manufacturing Engineering

Cite this

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title = "Measuring luminance and sun depression angle of dawn",
abstract = "Dawn are difficult to be seen when it first rises due to weather conditions and the low intensity of dawn light along with the factor of low visual acuity of the observer. In that case, the detection of the early emergence of dawn by using photometry is very important. The photometric device can detect and measure the dawn luminance, the moment it starts emerging. This study aims to measure the luminance of dawn, LD and the sun depression angle, D when the dawn began to appear by using a photometer, Sky Quality Meter (SQM) and Digital Single Lens Reflex (DSLR). The result of the measurement using these two tools were compared in terms of the luminance value and the measured value of the sun depression angle. The study was conducted from June to December 2017 in seven locations around Malaysia and Indonesia. The study found that the average value of LD is 19.47 mag arcsec -2 and 20.85 mag arcsec -2 with a DSLR and SQM, respectively. On the other hand, the average value obtained for D is -17.00° and -16.56° with DSLR and SQM, respectively. We therefore propose that LD is between 19.50 mag arcsec -2 and 20.90 mag arcsec -2 while D of the dawn is -17.00°.",
keywords = "Instrumentation: Photometer, Methods: Observational, Techniques: Image processing, Techniques: photometric",
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