About Hilal Vision
رؤية الهلال — Connecting Ancient Tradition with Modern Astronomy
Last updated: March 2026 · Version: 2.0
Overview
Hilal Vision is a precision astronomical platform purpose-built to predict and visualise the visibility of the Islamic crescent moon (هلال — hilāl) at any location on Earth. It serves 1.8 billion Muslims who rely on lunar reckoning for the commencement of Ramadan, Eid al-Fitr, Eid al-Adha, and every new Hijri month, as well as researchers, astronomers, and Islamic calendar scholars who study crescent observation methodology.
The platform synthesises three decades of peer-reviewed crescent visibility research — principally the Yallop (1997) and Odeh (2004) criteria — with real-time ephemeris data, live cloud-cover overlays, and a validated historical observation archive from the Islamic Crescents' Observation Project (ICOP), to produce visibility forecasts that are both scientifically rigorous and immediately accessible.
Mission
The Islamic lunar calendar is one of humanity's oldest living scientific traditions. For over 1,400 years, the commencement of each sacred month has been determined by the physical sighting of the new crescent moon. In the modern world, however, this practice is fragmented: different countries announce the beginning of Ramadan on different days, communities lack transparent data-driven tools, and the gap between astronomical possibility and religious authority creates avoidable confusion.
Hilal Vision exists to answer a single question with the precision it deserves:
"Will the new crescent moon be visible tonight from my location — and why?"
We implement the internationally recognised Yallop (1997) and Odeh (2004) visibility criteria — the same standards used by Islamic calendar authorities in the United Kingdom, Malaysia, Morocco, and the International Astronomical Center — and present the results with the visual clarity and interactivity expected by a 21st-century audience.
This platform is not a religious authority. It is a scientific instrument. It presents mathematical predictions, historical data, and comparative calendar analysis side-by-side, empowering individuals and communities to engage critically and transparently with Islamic timekeeping.
Who Is Hilal Vision For?
Muslim Communities
Get clear, location-specific predictions for crescent visibility before Ramadan, Eid, and every new Hijri month — without jargon or ambiguity. Understand why your local authority may announce a different date from a neighbouring country.
Astronomers & Researchers
Access raw q-values, ARCV/DAZ parameters, Odeh V-values, and the full ICOP historical dataset (1438–1465 AH, 1,000+ observations) for validation and academic research. Export data in CSV or JSON.
Islamic Calendar Scholars
Compare Astronomical (computed), Umm al-Qura (KACST), and Tabular Hijri calendars side-by-side. Understand precisely where and why civil calendars diverge from physical astronomical sighting.
Educators & Science Communicators
Use the 3D globe, 2D visibility heatmaps, and horizon simulator as pedagogical tools to explain the mechanics of crescent visibility to students.
Platform Overview
Hilal Vision is organised into six specialised astronomical tools:
| Tool | Description |
|---|---|
| 3D Globe & 2D Visibility Map | Interactive WebGL globe and Leaflet 2D map rendering crescent visibility zones worldwide using Yallop/Odeh q-values. Includes real-time cloud cover overlay and Best-Time-to-Observe engine. |
| Moon Phase Dashboard | Current lunar phase, illumination percentage, lunar age, topocentric coordinates, altitude/azimuth charts, 30-day phase strip, and Yallop/Danjon methodology charts. |
| Hijri Calendar | Three-engine calendar (Astronomical, Umm al-Qura, Tabular) with Gregorian cross-referencing, Islamic events, and a "Compare with Sky" layer. |
| Local Horizon View | Local horizon simulator showing crescent and solar positions at sunset, annotated with ARCV, DAZ, elongation, and Yallop q-value. |
| ICOP Archive | Full archive of 1,000+ verified historical crescent observations from the Islamic Crescents' Observation Project (1438–1465 AH). |
| Eclipse Tracker | Upcoming lunar and solar eclipses with visibility regions, peak times, and Islamic prayer guidance (Salat al-Kusuf / Salat al-Khusuf). |
Technology Stack
Hilal Vision is built on modern, performant web infrastructure:
| Technology | Role |
|---|---|
| React 19 + Next.js 15 (App Router) | Core framework, server components, Turbopack |
| Globe.gl + MapLibre GL | 3D WebGL globe and 2D interactive map |
| astronomy-engine (Don Cross) | VSOP87/ELP2000 planetary & lunar position algorithms |
| tRPC + Drizzle ORM + PostgreSQL | Type-safe API layer and relational database |
| Clerk Auth | Authentication, user management, and rate limiting |
| Capacitor.js | Native iOS & Android app packaging |
| react-i18next | 8-language internationalisation (EN, AR, UR, ID, MS, BN, FA, TR) |
| Serwist + PWA manifest | Offline-first service worker, push notification support |
| Open-Meteo API | Real-time cloud cover and atmospheric data |
| Stripe + RevenueCat | Payment processing (web and native) |
| Vercel | Global edge hosting and analytics |
Scientific Methodology Summary
Crescent visibility prediction is a multi-variable problem combining:
- Topocentric ephemeris — precise Moon and Sun positions (altitude, azimuth, elongation) computed at the observer's geographic coordinates using VSOP87/ELP2000 algorithms at local sunset
- Crescent width (W) — topocentric crescent width in arcminutes derived from the Moon's angular diameter and elongation
- Arc of Vision (ARCV) — the vertical angular separation between Moon and Sun at local sunset
- Yallop q-value — a composite visibility statistic mapping ARCV and W to six visibility zones (A–F)
- Odeh V-value — an independent visibility statistic derived from 737 ICOP observations, refining the Yallop model for telescopic and CCD sightings
- Danjon limit — a hard physical lower bound: crescent visibility is physically impossible when elongation < 7°, regardless of atmospheric conditions
- Atmospheric refraction — Meeus/Bennett correction applied to apparent altitude
- Cloud cover — live Open-Meteo data displayed as an overlay; atmospheric overrides (temperature, pressure) allow expert adjustment of refraction models
See the Methodology page for the full mathematical derivations and algorithm documentation.
Comparison with Existing Tools
| Feature | Hilal Vision | Moonsighting.com | IslamicFinder | HilalMap |
|---|---|---|---|---|
| Interactive 3D Globe | ✓ | — | — | — |
| 2D Global Visibility Map | ✓ | ✓ | — | ✓ |
| Live Cloud Cover Overlay | ✓ | — | — | — |
| Best-Time-to-Observe Engine | ✓ | — | — | — |
| Real ICOP Observation Archive | ✓ | ✓ | — | — |
| Crowdsourced Sighting Reports | ✓ | — | — | — |
| Three-Engine Hijri Calendar | ✓ | — | — | — |
| Scientific Parameters (q/V) | ✓ | ✓ | — | — |
| Multilingual (8 languages) | ✓ | — | ✓ | — |
| Animated Timeline | ✓ | — | — | — |
Table reflects publicly available features as of March 2026. ✓ = available, — = not available.
Data Sources & Attribution
Hilal Vision stands on decades of peer-reviewed astronomical research. All data sources and their contributions are fully disclosed:
Yallop (1997) Visibility Criterion
B.D. Yallop, HM Nautical Almanac Office, Royal Greenwich Observatory.
"A Method for Predicting the First Sighting of the New Crescent Moon."
Technical Note No. 69, 1997. PDF
→ Provides the q-value formula and six-zone classification system underpinning all Hilal Vision visibility maps.
Odeh (2004) Visibility Criterion
Mohammad Sh. Odeh, International Astronomical Center, Abu Dhabi.
"New Criterion for Lunar Crescent Visibility."
Experimental Astronomy, vol. 18, pp. 39–64, 2004. ResearchGate
→ Provides the V-value formula, trained on 737 ICOP observations covering visual, binocular, and CCD/telescope sightings.
Islamic Crescents' Observation Project (ICOP)
International Astronomical Center, Abu Dhabi.
→ Historical archive of 1,000+ verified crescent sighting observations spanning 1438–1465 AH, used in the ICOP Archive tool and for calibrating the Odeh V-value model.
ICOP Database
astronomy-engine (Don Cross)
Open-source VSOP87/ELP2000 planetary position library for JavaScript.
→ Used for all topocentric Moon/Sun position computations, providing sub-arcsecond accuracy.
GitHub · MIT License
Umm al-Qura Calendar (@umalqura/core)
KACST pre-computed tabular calendar for Saudi Arabia's official civil Hijri calendar.
npm
Open-Meteo
Free, open-source weather API providing real-time cloud cover data.
open-meteo.com
Meeus, J. (1998) — Astronomical Algorithms
Standard reference for atmospheric refraction correction formulas (Bennett correction).
Intellectual Property & Licensing
Hilal Vision is proprietary software. The brand, UI design system, code architecture, and proprietary data processing algorithms are the exclusive property of Hilal Vision.
- You may not copy, modify, distribute, reverse engineer, or sublicense any part of this platform.
- Third-party libraries (astronomy-engine, MapLibre GL, Drizzle ORM, etc.) are used under their respective open-source licences (MIT, Apache 2.0). Attribution is provided above.
- ICOP data is used with attribution to the International Astronomical Center.
- Yallop and Odeh criteria are published scientific formulas in the public domain; their implementation in Hilal Vision is original.
See LICENSE in the repository root for the full proprietary licence text.
Contact & Feedback
Found a bug, have a question about methodology, or want to contribute observation data?
- Contact page: moonsighting.live/contact
- Email: support@moonsighting.live
We welcome feedback from the astronomical and Islamic scholarly community.