Jakarta –
The start of Ramadan is always a moment that Muslims in Indonesia look forward to. Scientifically, this determination is not only based on naked eye observations, but involves precise astronomical calculations.
For the year 1447 Hijriah or 2026 AD, scientific data shows the potential for differences in the start of fasting due to differences in the criteria used. How does science predict the start of Ramadan?
Let’s dissect it based on data from the National Research and Innovation Agency (BRIN) and the Meteorology, Climatology and Geophysics Agency (BMKG).
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Difference in Criteria: Local Hilal vs Global Hilal
Table of Contents
Coordinator of KR Astronomy and Observatory at the BRIN Space Research Center, Prof. Thomas Djamaluddin explained that this year’s differences were not triggered by the unclear position of the new moon, but rather differences in the criteria for reaching the new moon.
“There will be differences in determining the start of Ramadan 1447. The source of the differences is not, as before, related to the position of the new moon, but more due to the difference between ‘local new moon’ and ‘global new moon’,” said Djamaluddin when contacted, Thursday (5/2/2026), as reported Detik news.
1. Local Hilal Criteria (MABIMS)
Used by the Government (Ministry of Religion) and the majority of Islamic mass organizations. This criterion requires that the crescent moon must be visible in Indonesian territory with a minimum height standard of 3 degrees and an elongation of 6.4 degrees.
2. Global Hilal Criteria
Used by Muhammadiyah. In principle, as long as the crescent moon meets the visibility criteria in any part of the world and the conjunction occurs before dawn in New Zealand, then the new moon has entered.
Astronomical Analysis
Based on BMKG data, a geocentric conjunction event (when the positions of the Moon and Sun are at the same ecliptic longitude) is predicted to occur on Tuesday, February 17 2026, at 19.01 WIB.
Scientifically, this is a crucial point. Because the conjunction occurs after sunset in Indonesia, in the evening:
- The position of the new moon is still below the horizon (minus).
- The height of the crescent moon ranges from -2.41° in Jayapura to -0.93° in West Sumatra.
- The age of the moon is still negative, meaning that physically the crescent moon will not be born when the sun sets.
Therefore, for users of the Local Hilal criteria, the month of Syakban will be completed (istikmal) to 30 days, so that 1 Ramadan 1447 H is predicted to fall on 19 February 2026.
On the other hand, users of Hilal Global criteria look beyond national borders. Prof. Thomas said that on February 17, the moon’s position met the visibility criteria in Alaska, United States.
Because the conjunction occurred before dawn in New Zealand and the new moon already “exists” globally, this group most likely determined that 1 Ramadan 1447 AH falls on February 18 2026.
For people who are waiting for the results of the government’s isbat session, the new observation (rukyat) will be effective on February 18 2026 evening. At that time, scientific data showed that the position of the new moon was very mature:
- Hilal Height: Has reached 7.62° in Merauke to 10.03° in Sabang (far beyond the 3° requirement).
- Elongation: Ranges from 10.7° to 12.21° (exceeds the requirement of 6.4°).
- Moon Age: Has reached 20 to 23 hours.
With such a high position, the crescent moon will certainly be very easy to see through a telescope or the naked eye if the weather is clear.
Even though scientific calculations (hisab) have provided a very clear picture, the Indonesian Government will still hold an Isbat Session on February 17 2026. This session functions as a formal confirmation between mathematical calculations and field facts through rukyatul hilal.
Science does not aim to emphasize differences, but rather provides objective data so that people understand why these differences occur. As stated by Prof. Thomas Djamaluddin, astronomically there is no wrong data; differences arise only because of differences in believed criteria.
(hh/message)
date:2026-02-14 10:00:00