Maximum tides in coastal areas need to be a concern because they often cause tidal flooding. Analysis of maximum tides on the west coast of Sumatra uses long-term data from Sabang 13 years (2005–2018), Sibolga 28 years (1989–2004, 2005–2018), and Padang 25 years (1986–1998, 2005–2018). The analysis of maximum tides is associated with the analysis of the lunar and solar astronomical parameters that influence them. In general, the daily tide pattern has a semi-diurnal pattern which is related to the influence of the lunar phases which is clearly indicated by the monthly variation pattern. Maximum tides reach their peak during the new and full moon which is strengthened by lunar perigee conditions. Spectral analysis shows a semi-annual dominant period which is influenced by variations in solar declination. This is also shown by the annual variation of maximum tides which peak around June when the sun is most north (maximum declination 23.5°) and around December when the sun is furthest south (minimum declination −23.5°). There is no indication of the 18.6 years variation due to the lunar nodal cycle. Maximum tides are dominantly influenced by the moon phase, the nearest distance between the moon and the earth (perigee), and the sun’s declination, which can be an early warning of potential flooding. The tidal flood on Padang coast on June 6 2024 is related to the new moon (June 6), perigee (June 2), and the northernmost sun (June).

Determining the Beginning of Fajr Time is an important issue that requires synergy between scientific and shar‘i approaches. The fajr ṣādiq (true dawn) as the indicator marking the beginning of Fajr time has become the main focus of various astronomical studies and fiqh discussions. However, the criteria for determining Fajr time remain a matter of debate to this day. This study employs a qualitative-descriptive approach through library research to reconstruct the paradigm of dawn observation based on the integration of astronomy (‘ilm al-falak) and Islamic jurisprudence (fiqh). The findings show that the paradigm for determining the beginning of Fajr time is grounded in identifying the earliest, most accurate, and objective appearance of the fajr ṣādiq. The analogical approach to determining the beginning of the Hijri month reinforces the scientific principle of dawn observation, namely the use of the lowest threshold criterion in identifying the first astronomical phenomenon that signifies a change in time. The application of this principle, as adopted by LF PBNU, reflects a shared paradigm between science and fiqh in affirming the boundaries of worship times both empirically and normatively.

Prayer times are extremely important for Muslims, as they serve as a guide for the beginning of prayer times. However, there are still people who do not fully understand the impact of changes in the position of the Sun, which causes the start of prayer times to change daily. Additionally, some people still use perpetual prayer time schedules. Although they use the term "perpetual," in reality, prayer time schedules are not everlasting, as they cannot be used over long periods. This research is a library study with a phenomenological-astronomical approach. The results of this study show that prayer times change every day. Someone who believes that the start of Maghrib prayer is always at 18:00 WIB and the start of Fajr prayer is always at 04:30 WIB may find that on some days, their prayer or fasting is invalid, as the start of Maghrib prayer may occur between 18:01 and 18:08 WIB and the start of Fajr prayer may occur between 04:31 and 04:34 WIB. These changes can serve as an understanding for the community that the correctness of prayer time schedules is not static-passive but dynamic-variable. This means that the start of prayer times each day and year is not always the same as the following days and years, and the changes vary. Therefore, this study provides a scientific guide for the community to better understand and be cautious in using prayer time schedules, considering that the beginning of prayer times determines the validity of a Muslim's prayer.

A new observatory site should be investigated for its local climate conditions to see its potential and limitations. In this respect, we examine several meteorological parameters at the site of Timau National Observatory, Indonesia using the ERA5 dataset from 2002 to 2021. Based on this dataset, we conclude that the surface temperature at Timau is around 18.9 C with a relatively small temperature variation (1.5 C) over the day. This temperature stability is expected to give advantages to the observatory. In terms of humidity and water vapour, Timau is poor for infrared observations as the median precipitable water vapour exceeds 18 mm, even during the dry season. However, near-infrared observations are feasible. Even though our cloud cover analysis confirms the span of the observing season in the region, we find a significant discrepancy between the clear sky fraction derived from the ERA5 dataset and the one estimated using satellite imagery. Aside from the indicated bias, our results provide insights and directions for the operation and future development of the observatory.

This article aims to present a digital visualization of the new moon (hilal) as a determinant of the beginning and end of Ramadan fasting, exploring the astronomical phenomenon of hilal visibility during the Prophet Muhammad's era using the Digistar 6 system in a planetarium. Several Islamic jurisprudence (fiqh) literatures discuss comparisons of fasting durations during the Prophet's time, ranging between 29 and 30 days. This study employs a qualitative research method based on library research, utilizing an astronomical approach and simulation observations in a planetarium. The data used include historical and astronomical data from the Prophet Muhammad's era, as well as related classical literature. The findings of the study include the integration of Digistar 6 technology with computational data to reconstruct the hilal phenomena of the Prophet’s time. For instance, the elevation of the hilal marking the beginning of Syawal in 8 AH was observed at a minimum Moon Altitude of 02°06’22” above the horizon, with an elongation of 04°55’56” and an atmospheric clarity of 9.52%. The Prophet Muhammad observed Ramadan fasting nine times, with six instances involving 29 days of fasting and the remaining three involving 30 days, as determined through simulated physical imagery of the hilal.

The short-lived tropical squall lines could trigger weather-related hazards to the northern part of the Indonesia Maritime Continent (IMC), such as Sumatra and Kalimantan. Herein, we investigated the rare propagation event of the long-lived Sumatra squall line associated with a severe storm surge that induced coastal inundation in Java-Bali with devastating impacts from 22 May-2 June 2020. With a comprehensive approach combining observational, numerical, and analytical studies, for the first time, we proposed the possible mechanism related to the long-lived squall line over the IMC, which represents the largest equatorial tropical region with the most complicated air-sea interaction area in the world. Our findings suggest that the long-lived squall line related to the supercell-like thunderstorm initiated from multicell over central Sumatra on May 20, 2020, continuously propagated southeastward until several days later reached Bali. The near-quasi steady convective line has 6 hours of time travel from central Sumatra to west Java. The supercell-like rapidly develops from multicell with a deep convective updraft under the strong and fast cold pool (similar to 13.8 m s(-1)). The further southeastward propagation of squall line with broken line type seems reinforced by low-level moist transport from the Java Sea. This study also suggested that this unusual event of a long-lived squall line might occur more frequently in the warming upper ocean in the IMC.

It has been analyzed 285 light curve SQM (Sky Quality Meter) data for night sky conditions until dawn in clear conditions and without moonlight interference in 20 locations. The observation locations were divided into four categories: dark, slightly dark, slightly bright, and bright. By comparing the darkness of the observation locations, it is concluded that the visibility of the zodiacal light and the astronomical twilight is affected by light pollution. Statistical analysis shows that 77% of astronomical twilight is affected by light pollution at the observation site. The impact of light pollution on the sun's altitude at dawn is described by the equation y=0.55 x+11.12 ± 1.45, where y is the brightness of the night sky (in mpsas) and x the sun's altitude at the beginning of twilight (in degrees). This equation means that if there are reports of the beginning of twilight when the sun's position is higher, it is caused by light pollution which causes the sky getting brighter. This study obtained that the average sun's altitude at the beginning of twilight in the dark area is −19.40 ± 0.53 degrees. Light pollution also affects the appearance of the zodiacal light. The appearance of the zodiacal light is indicated by the slope pattern of the light curve which shows that the eastern horizon is slowly getting brighter. In dark areas, the zodiacal light is clearly visible with a linearly decreasing light curve pattern. In bright areas, the slope pattern does not exist because light pollution dominates with a constant pattern.

This study aims to integrate hadith , astronomy and sociology studies in examining the implementation of Hijri calendar unification through a multidisciplinary approach. The Hijri calendar is based on the astronomical phenomena of the earth-moon-sun system and should refer to the provisions of Islamic law or fiqh to be implemented in worship. For the preparation of a good Hijri calendar, agreement on criteria, date line, and authority is necessary. Furthermore, agreement on criteria requires a valid argument based on astronomical studies. An agreement on the implementing region boundaries is necessary due to the round earth and the hilal [crescent moon] cannot be observed simultaneously anywhere. It is also needed to resolve unavoidable differences, specifically in the appearance of the hilal and in schools of Islamic law. The problems to be solved are as follows: What is the strategy for implementing Hijri calendar unification? This study is based on a review of hadith and fiqh literature, analysis of astronomical data related to criteria, and experiences of Indonesia and Islamic countries regarding the Hijri calendar unification. The results show that implementing the Hijri calendar unification through the three approaches above can be carried out and accelerated. Contribution: This study contributes to showing the results of a multidisciplinary approach in the problem of implementation of the new Ministers of Religious Affairs of Brunei Darussalam, Indonesia, Malaysia, and Singapore (MABIMS) criteria towards unification of the Hijri calendar.

In this work, the dynamics of one particular fibril were investigated through high-resolution multi-wavelength images with high cadence obtained from the Dutch Open Telescope. Based on exceptional observation data of Active Region 10789, 13th July 2005, we investigated the alternating fibril pattern using tomography of the multi-wavelength band, consisting of the hydrogen alpha line center and also the blue wing, the calcium II H line, and the G-band. Phase difference and coherence analyses were conducted for several points along the fibril and (k, ω) analysis was conducted to understand the wave interaction and its mechanism in the propagation process. Our findings suggest short- to long-period transitions along the fibril with coherence in 10-min oscillations in the penumbra.

A satellite placed in space is constantly affected by the space environment, resulting in various impacts from temporary faults to permanent failures depending on factors such as satellite orbit, solar and geomagnetic activities, satellite local time, and satellite construction material. Anomaly events commonly occur during periods of high geomagnetic activity that also trigger plasma variation in the low Earth orbit (LEO) environment. In this study, we diagnosed anomalies in LEO satellites using electron data from the Medium Energy Proton and Electron Detector onboard the National Oceanic and Atmospheric Administration (NOAA)-15 satellite. In addition, we analyzed the fluctuation of electron flux in association with geomagnetic disturbances 3 days before and after the anomaly day. We selected 20 LEO anomaly cases registered in the Satellite News Digest database for the years 2000–2008. Satellite local time, an important parameter for anomaly diagnosis, was determined using propagated two-line element data in the SGP4 simplified general perturbation model to calculate the longitude of the ascending node of the satellite through the position and velocity vectors. The results showed that the majority of LEO satellite anomalies are linked to low-energy electron fluxes of 30–100 keV and magnetic perturbations that had a higher correlation coefficient (~ 90%) on the day of the anomaly. The mean local time calculation for the anomaly day with respect to the nighttime migration of energetic electrons revealed that the majority of anomalies (65%) occurred on the night side of Earth during the dusk-to-dawn sector of magnetic local time.

In this work we continue our previous work on wave propagation analysis using multi-wavelength images from Dutch Open Telescope from exceptional data observed of Active Region 10789, 2005 July, 13th. By Fourier analysis we study the layer by layer interaction of the Solar atmosphere represented by multi-wavelength, consist of Hα both line center & the blue wing, Ca II H, and the G Band. By Fourier decomposition from power, coherence and phase-difference along the fibril we try to discuss the possible mechanism in the area under investigation.

In this work we selected one particular fibril from a high resolution observation of the solar chromosphere with the Dutch Open Telescope, and tried to obtain a broad picture of the intricate mechanism that might be operating in the multiple layers of the solar atmosphere visible in high cadence multi-wavelength observations. We analyzed the changing fibril pattern using multi-wavelength tomography, which consists of both the Hα line center and the blue wing, Doppler signal, Ca II H, and the G-band. We have found that the intermittent ejected material through the fibril from Doppler images has clearly shown an oscillation mode, as seen in the Hα blue wing.The oscillations in the umbrae and penumbrae magnetic field lines that are above the sunspot cause a broadening and the area forms a ring shape from 3 to 15 minute oscillations as a function of height. These made a distinct boundary between the umbrae and penumbrae which suggests a comb structure, and indicates that the oscillations could propagate along the inclined magnetic flux tubes from below. The 3 minute oscillations strongly appeared in the broadly inclined penumbrae magnetic field lines and showed a clear light bridge. The well known 5 minute oscillations were dominant in the umbrae-penumbrae region boundary. The long 7 minute oscillations were transparent in the Hα blue wing, as well as the 10 and 15 minute oscillations. They were concentrated in the inner-penumbrae, as seen in the Hα line center. From these findings we propose that the fibril acts as a fabric for interaction between the layers,as well as related activities around the active region under investigation.

This study using data of hilaal observation compiled by the Ministry of Religious Affairs (MORA) Republic of Indonesia during 1962-2011 period, the observational data of Rukyatul Hilal Indonesia (RHI) during 2007-2009 period and Odeh’s international observational data during 1859-2005 period. Those data were selected by applying selection procedure of Djamaluddin (2001) and by eliminating hilal data whose angular distance < 3° between hilaal and particular planet. Next, selected data were plotted to graphic of Sun-Moon altitude difference (ARCV - Arc of Vision) and Sun-Moon angular distance (ARCL - Arc of Light), moon age and Sun-Moon angular distance (ARCL - Arc of Light) and Sun-Moon altitude difference (ARCV - Arc of Vision) and Sun-Moon angular distance (DAz - Delta Azimuth) to propose the new hilaal visibility criteria in Indonesia. The new criteria proposed are ARCL greater than 5.4°, Moon is as old as 9.4 hours after conjuction and = 3° if DAz 5° ARCV -0.719(DAz)+6.795 if DAz < 5°    .