Introduction

This Hilal Position Calculator ver. 2.2009 is the first version published in 2009 for public use in Malaysia. The calculation uses the method in the book Ilmu Falak by Baharrudin bin Zainal published by DBP in 2002. As stated by the author of the book, the calculation is based on low-precision methods and suitable for general reference only. Furthermore, this Hilal Position Calculator is NOT AN OFFICIAL SOFTWARE of the authorities involved in compiling the calendar.

This calculator performs calculations in stages.

Stage one (1) calculates the position of the crescent moon according to selected criteria for determining the beginning of the month (1st) of the previous month.

Stage two (2) Based on the date of the 1st day of the previous month, the 29th day can be determined.

Stage three (3) calculates the position of the crescent moon for that 29th day, then displays important reference data and illustrative diagrams. If the calculation indicates that the crescent moon does not meet the chosen criteria on the 29th day, data for subsequent days will also be displayed.

Please note that this calculation is NOT based on the actual reference location of any country, but rather uses YOUR CHOSEN LOCATION. Therefore, the data display may differ from the official local calendar.

Illustrations of the positions of the moon and sun are displayed for basic visualization according to scale.

Definitions:

• Criterions: Conditions for the justification of the crescent moon is 'visible' or 'not visible'.
  • Malaysia 1992: Criteria used from 1992 to 2021 (1442) in Malaysia. Abolished in 2021 (1443).
  • Malaysia 2021: Also known as KIR 2016. New criteria starting in 2021 (1443) in Malaysia.
  • Istanbul 1978: Criteria resulting from the conference in Istanbul in 1978. Abolished in 1992.
  • Odeh 2005/2006: One of the criteria used by Mohammad Odeh (www.icoproject.org) for justifying the appearance of the crescent moon. Used on this site under the assumption of representing international criteria.
• Conjunction Date and Time: Date and time of the conjunction of the moon and sun, based on the location and GMT entered.
• Sunset: time of sunset at the horizon.
• Moonset: time of moonset at the horizon.
• Moon Altitude: angle of the moon's height calculated from the horizon. Altitude values ​​are given observed altitude and true/apparent altitude.
• Elongation: the angle of separation between the moon and the sun. The calculation is from the center to the center of the object's disk. Using observed altitude values ​(topocentric elongation). While using true altitude values, it is called geocentric elongation.
• Moon Azimuth: the direction of the moon's position in degrees calculated from the North in clockwise rotation along the horizon circle.
• Sun Azimuth: the direction of the sun's position, in the same angle as the moon.
• Visible Duration: the difference in time between the time of moonset and sunset. If the moon sets first, there is no visible period.
• Moon Age: refers to the period of time after the conjunction occurs. The age from the time of conjunction to the time of moonset is used as one of the conditions for imkanurrukyah. The value in negative refers to the conjunction not yet occurred (remaining time period before the conjunction occurs - last phase moon/waning crescent).
• Illumination: refers to the percentage of the illuminated moon's surface visible from the observation location. 100% refers to the full moon phase.
• SD: Semi-diameter of the moon (moon disk radius).
• Moon-Earth Distance: the distance from the moon to the earth in kilometers.

Hope this is helpful.

Thank you.

Ahmad Taufan bin Abdul Rashid

10 Feb 2009 (updated Sep 2011, Jun 2020, Sep 2021, Jul 2023, 2026)