🌙 HilalNama — Scientific Assistant for Crescent Moon Calculation and Observation

Hilal-Nama is a specialized application for precise astronomical calculation of new crescent moon (Istihlal) visibility; a tool useful both for amateur observers and astronomy enthusiasts, and for religious students, researchers, and official crescent-sighting commissions who need accurate, citable astronomical data.

Unlike ordinary lunar calendars that simply display a fixed date, Hilal-Nama calculates — based on the actual positions of the sun and moon at the moment of sunset, for the user's precise geographic location — whether the crescent is visible at all on that day and at that point on Earth, whether with the naked eye or only with optical aid.

🔭 Calculation Based on 6 Internationally Recognized Scientific Criteria

HilalNama simultaneously calculates and compares the result based on six criteria recognized in the astronomical literature on crescent visibility:

• Yallop (1997) — Royal Greenwich Observatory, based on 295 historical observations
  
• Odeh (2004/2006) — based on 737 Arab and Islamic observations
  
• SAAO / Caldwell & Laney (2001) — South African Astronomical Observatory
  
• Ilyas (1988)
  
• MABIMS 2021 (Neo-MABIMS) — the official criterion of Malaysia, Indonesia, Brunei, and Singapore (adopted December 8, 2021)
  
• Soroudi ★ — the app's own proposed hybrid criterion, which takes its base classification from Yallop and also shows the level of agreement among independent witnesses (SAAO and Ilyas); explicitly marked in the app as an unofficial, proposed criterion (not a global standard)
  

For each criterion, its reference scientific explanation and result category (from easy naked-eye visibility to non-visible) are displayed separately, and in cases where criteria disagree on borderline days, the app explains this to the user as a recognized scientific fact (not an error).

📊 Precise and Complete Astronomical Data

For every day and location, Hilal-Nama calculates and displays a complete set of astronomical parameters related to crescent visibility, including:

• Exact time of sunset and moonset (based on the city's real time zone)
  
• Altitude and azimuth of the moon and sun at the moment of sunset
  
• Difference in azimuth (DAZ) and relative arc of vision (ARCV)
  
• Moonset lag time relative to sunset (Lag Time)
  
• Age of the crescent from the moment of conjunction (Age)
  
• Percentage of crescent illumination (Illumination)
  
• Crescent width in arcminutes
  
• Angular distance between sun and moon (Elongation) — both topocentric and geocentric
  
• Moon's distance from Earth, moon's ecliptic latitude
  
• Checking the Danjon Limit both for the naked eye and for telescope observation
  
• Calculation of the exact moment of conjunction (Conjunction / New Moon)
  
• Automatic warning for polar regions under midnight-sun or polar-night conditions, where crescent visibility calculation is not meaningful
  

Users can switch between four key days of each lunar month (the day before conjunction, the day of conjunction, the day after, and two days after conjunction) and view the result for each separately.

🗺️ Global Crescent Visibility Map

One of the app's core sections is the interactive global crescent visibility map, drawn based on the real borders of the world's countries (not approximate continental shapes). This map shows in color what the crescent's status is at every point on Earth, based on the selected criterion (ranging from easy visibility to non-visible). Features of this section include:

• Zooming and panning the map with touch gestures (pinch to zoom)
  
• Display of major cities and populous Muslim-majority countries along with their flags
  
• A finer grid mode in landscape display for greater detail
  
• A complete astronomical info card for each city upon tapping the map
  
• Comparison of the user's city status with other cities around the world at a glance
  
• A guide to the colors and categories of the selected criterion
  

🔬 Advanced Crescent Analysis

For more advanced users, Hilal-Nama has an advanced analysis page that includes:

• Interactive sky simulation with the ability to play/pause the movement of the sun and moon over time
  
• A timeline chart of key parameters (moon altitude, sun altitude, ARCV, angular distance, crescent width) with the ability to toggle each on/off as a separate layer
  
• Comparison of two time moments to see the exact difference in parameters
  
• An automatic plain-language text summary of the visibility status
  
• Complete astronomical data, grouped and collapsible, for examining the finest details
  

📝 Recording and Reviewing Crescent Observation Reports (Social Section)

HilalNama is not just a calculator; it also provides the ability to record actual crescent observation reports:

• Recording an observation report including name, email (optional), country/province/city of observation, precise geographic coordinates (optional), altitude of the location, exact date and time of observation (solar and Gregorian calendars), observation result (sighted or not sighted), reason for not attempting (if applicable), equipment used, weather conditions, horizon quality, cloud cover percentage, and free-text notes
  
• Each user can submit one report per lunar month and can edit their own report
  
• Browsing other users' reports filtered by lunar month and country, with search and filtering by observation result (sighted / not sighted / all)
  
• Displaying the calculated astronomical data alongside each report, for comparing actual observation with the scientific prediction
  

📄 PDF Report Output for Crescent-Sighting Commissions

HilalNama provides the ability to generate a complete, professional PDF report that can be used for submission to official crescent-sighting commissions. Users can customize the report content:

• Choosing which of the 4 key days of the lunar month to include in the report
  
• Adding the global visibility map (with two quality levels: fast or more precise) based on one or more criteria
  
• Adding a complete table of astronomical data
  
• Adding a comparison table of the different criteria
  
• Adding an explanatory guide to the criteria
  

The final output is a PDF file ready for sharing or saving.

📚 Crescent Observation Educational Guide

The "Guide" section offers a structured course (module → section → lesson) on the science and practice of crescent observation; including astronomical fundamentals, an introduction to scientific visibility criteria, and practical field observation tips — for those who want to understand the scientific logic behind these calculations, beyond just numbers and charts.

⚙️ Other Features and Settings

• Selecting the observation location from a list of major world cities (with search and filtering by country) or manually entering geographic coordinates
  
• Three complete languages: Persian, Arabic, and English, with full right-to-left (RTL) support
  
• Sharing the result as a text summary (including date, city, each criterion's result, and technical crescent specifications) with other applications
  
• Smart reminders (local notifications) before probable crescent-sighting dates in upcoming months
  
• Server connection status warning in the report submission/browsing section, for complete transparency with the user
  

Disclaimer:

HilalNama is a computational-scientific tool, and its results are calculated based on internationally recognized astronomical models; however, actual crescent visibility always depends on atmospheric conditions, the real horizon, and observation circumstances, and the final calculation results are not a substitute for actually sighting the crescent moon.