Frequently Asked Questions

Yes. Traditional methods use a fixed geometric angle (typically 18°) to estimate Fajr time. Takbir is the first to use Monte Carlo radiative transfer simulation, the same physics used in climate science and astrophysics, to calculate when dawn light actually becomes visible through the real atmosphere.

The simulation accounts for real atmospheric conditions that traditional methods ignore: cloud cover, aerosols, pollution, temperature profiles, surface albedo, and more. While absolute validation is ongoing, the physics correctly models the direction and magnitude of weather effects on twilight visibility.

Absolutely. On a clear day, twilight light passes through the atmosphere relatively unimpeded. On a heavily overcast day (optical depth 30+), thick clouds block 99.99% of scattered light, meaning the "white thread" becomes visible later. Our simulation can shift Fajr by up to 10-90 minutes based on actual weather conditions.

We combine data from multiple sources: Met.no for cloud coverage, GFS/Open-Meteo for atmospheric profiles (temperature, humidity, pressure at 19 altitude levels), CAMS satellites for aerosol optical depth, SRTM for terrain elevation, NOAA IMS for snow cover, and NASA JPL DE440 for precise solar positioning.

Takbir can calculate Fajr for any location on Earth where atmospheric data is available. The simulation takes your latitude, longitude, elevation, and local atmospheric conditions into account.

SMART-G (Speed-Up Monte Carlo Advanced Radiative Transfer code with GPU) is the radiative transfer engine at the core of our simulation. It was developed by CNRS/Laboratoire d'Océanographie de Villefranche and traces photon paths through atmospheric media with full scattering and absorption physics.

Takbir is a scientific tool that aims to more accurately fulfill the Quranic criterion for Fajr. Classical scholars determined Fajr through direct observation of dawn light. Our simulation is the computational equivalent of that observation, applied consistently and scientifically. We encourage users to consult their local scholars.

The 18° convention assumes a clear, uniform atmosphere with no clouds, pollution, or aerosols. In reality, atmospheric conditions vary dramatically by location, season, and weather. A thick overcast sky can delay visible dawn significantly compared to a clear sky at the same solar angle. The fixed-angle approach ignores all of this.

Each run traces over 2 million photons across 41 wavelengths (300-700nm) and 49 sun angles (0° to -24° below the horizon). The full precomputed dataset covers over 40 billion photon paths. All of this runs on GPU-accelerated hardware using the SMART-G engine.

Instead of shooting photons from the sun and hoping some reach the observer (extremely inefficient), we trace photons backward from the observer's eye into the sky. Each photon bounces through the atmosphere, scattering off molecules and cloud droplets, until it either reaches the sun or gets absorbed. This is the same technique used in movie CGI rendering.

Yes. We use SRTM elevation data to determine the observer's true altitude above sea level, which affects the atmospheric path length and the geometric horizon. A mountaintop observer sees dawn earlier than someone in a valley.

Snow-covered ground reflects significantly more twilight light back into the atmosphere (high surface albedo). This reflected light scatters again, making dawn appear brighter and earlier than it would over dark terrain. Takbir uses NOAA IMS satellite data to detect snow and ice coverage around the observer.

We are planning to release the code as soon as possible. The simulation engine, methodology, and all atmospheric data sources are fully documented on this site. We believe transparency is essential when the output affects religious practice. The goal is for anyone to understand, verify, and reproduce the results.