Tell the page which Islamic date an English date falls on, for the selected month. Example: set 10 October 2026 = 28 Rabi al-Thani 1448, and the 29th evening becomes 11 October 2026 (the 30th evening, 12 October). The table only ever shows the 29th or 30th evening.
Confirm the month length
Once the moon is sighted (or not), confirm whether this month had 29 or 30 days. The month list then shows the length and the last day for this month.
Export site data (for hosting on your own site)
Downloads the month dates, month lengths, custom cities, verses and FAQ as hilal-data.json. Upload it next to the standalone page. Sighting reports and images are not included.
Moon position chart (direction vs altitude at sunset)
Plots Lilongwe, Harare, Windhoek, Musina, Gaborone, Polokwane, Pretoria, Kimberley, Durban and Cape Town by the moon’s direction (azimuth) and altitude at sunset. The crescents point toward the sun and their thickness follows the illuminated percentage (slightly exaggerated so they stay visible). The axes fit the cities automatically.
Poster for a town (29th evening)
Pick a town. The poster shows that town’s parameters for the 29th evening of the month selected above, ready to download as an A3 PDF for printing.
Use this where the 29th Islamic day falls a day earlier or later than shown. The sunset, moon and Yallop details are recalculated for that date.
If you change either date, it shows an asterisk (*) and a note at the bottom of the poster says it was adjusted.
Admin: poster verses
Each poster uses a randomly chosen verse. Two built-in verses are always included. Add more here.
Tentative dates for an Islamic year
Calculates the expected start of Ramadan, Eid ul Fitr, Dhul Hijjah and Eid ul Adha. Starting from the month already confirmed on this page, each following month is counted as 29 or 30 days depending on whether the moon is expected to be sighted on the 29th evening. Earlier years are counted back from the same month. Any date overrides or confirmed month lengths set by the admin are used automatically. Tentative only.
Sighting reports (29th evening)
Report what you saw on the 29th evening. Reports from around the region appear on the map below, which can be downloaded as a PDF to share. The admin decides which reports are included.
Report a sighting
Your access to this page is view only, so reports can’t be saved from here. Use “Copy report text” and send it to the admin, who can add it for you.
Crescent image for the PDF (admin)
Add a photo of the crescent and say where and when it was taken. The moon’s altitude, elongation, illumination, sunset and moonset are then calculated and printed next to it on the PDF. The image is only used for the PDF and is not stored.
Image titler (label your horizon photo)
Upload a photo of the horizon, confirm where and when it was taken, and the moon’s elevation, elongation, illumination, sunset, moonset and the Islamic date are stamped on it. The photo stays on your device. It is not uploaded or saved anywhere.
Choose a photo
Horizon simulation (where to look for the crescent)
Starts 10 minutes before sunset and plots the sun at sunset, then the moon when the sun is 3° below the horizon and about every 10 minutes after that until moonset, on an azimuth and altitude grid. Bright planets and stars nearby are marked so you can use them as reference points. You can add your own horizon photo as the background. The photo stays on your device.
Admin: presets with image
Set the location, choose a horizon photo, align it with the controls below, then save it here for everyone. To change a preset, select it in “Location – preset with image”, adjust the controls and choose “Update settings”. To swap the photo, choose a new file and “Replace image”.
Align your photo to the grid
Set the azimuth at the middle of the photo (you can also drag the image with the mouse), how many degrees wide the photo is, where the horizon sits in the photo, and straighten it with rotate. Check against a point you know, such as 270°.
Use the alignment controls so the horizon in your photo sits on the 0° line and a known direction lines up with its azimuth line. Positions are calculated for a clear, flat horizon. The grid, not the photo, is the accurate part.
Frequently asked questions
Ask a question
Type a question about the moon, the crescent or how to use this page, and an AI assistant will answer it. AI answers can contain mistakes and are not an official ruling.
Add a question (admin)
Add a city (admin)
Yallop criterion and method
Regions. Southern Africa (the default) uses the dates confirmed and adjusted by the HilalWatchZA admin. Other regions work out their own Islamic month from the calculation for that region: the first evening on which the crescent is expected to be visible (Yallop code A–C) from the region’s reference cities starts the new month. Türkiye follows the Diyanet criteria, and the Middle East follows the Umm al-Qura rule used in Saudi Arabia. Local moon-sighting committees and national authorities may announce a different day.
Yallop (1997): at the best time (sunset + 4/9 of the lag to moonset) the app takes ARCV, the geocentric altitude difference between the moon and sun, and the crescent width W in arc minutes. It then computes q = (ARCV − (11.8371 − 6.3226W + 0.7319W² − 0.1018W³)) / 10.
A q > +0.216 easily visible · B q > −0.014 visible under perfect conditions · C q > −0.160 may need optical aid to find the crescent, then visible to the naked eye · D q > −0.232 will need optical aid · E q > −0.293 not visible with a telescope · F below that: not visible, below the Danjon limit.
Sunset, moonset, altitude, azimuth, elongation, lag and age are computed as in your script (sea level, standard refraction). If the moon sets before the sun, q is calculated at sunset. If the new moon has not yet occurred, no Yallop value is shown.
Glossary of terms
Altitude (elevation)
How high something is above the horizon, in degrees. 0° is the horizon and 90° is straight up. The app uses the moon’s apparent altitude, which includes the bending of light by the atmosphere (standard refraction).
Azimuth (direction)
The compass direction of the moon or sun, in degrees measured clockwise from true north: 0° is north, 90° east, 180° south and 270° west.
Elongation
The angle in the sky between the centres of the moon and the sun. It is zero at new moon and grows as the moon moves away from the sun. A larger elongation generally means a brighter, easier crescent.
Illumination
The percentage of the moon’s visible disc that is lit by the sun. A young crescent is typically only a few percent lit.
Moon age
The time since the new moon (conjunction) at the moment shown, usually at sunset. A moon that is only hours old is very hard or impossible to see.
Birth of the moon (new moon, conjunction)
The moment the moon passes between the earth and the sun, and the new lunar cycle begins. The crescent can only be seen after this.
Lag time
The number of minutes between sunset and moonset. If it is short or zero or negative, the moon sets with or before the sun and cannot be seen.
Astronomical sunset and moonset
The moment the upper edge of the sun or moon touches the horizon, at sea level, allowing for standard refraction. Local times can differ slightly from printed timetables.
Sun 3° below the horizon
The sun is 3° below the horizon about 12–15 minutes after sunset, depending on place and season. The sky is dark enough for a faint crescent to show but still bright enough to see the horizon. The tables and the Horizon simulation use it as the time to start looking.
Best time
In the Yallop method, sunset plus 4/9 of the lag time. It is the moment the crescent is most likely to be seen.
ARCV (arc of vision)
The difference in altitude between the moon and the sun at the best time, measured from the centre of the earth (geocentric). A larger ARCV means the moon is higher above the sun’s position.
W (crescent width)
The width of the lit crescent at its widest, in arc minutes (1/60 of a degree). It depends on the moon’s size and distance and on the elongation.
q value and Yallop code
A number worked out from ARCV and W. It is turned into a code from A (easily visible) to F (not visible). See the key above.
Danjon limit
The smallest elongation, about 7°, below which the crescent has never been reliably seen. Code F means the moon is below this limit.
Naked eye, binoculars, telescope
Code A to C crescents can be seen with the eye (code C may need optical aid to find them first). Code D needs optical aid, and E can only be seen with a telescope under very good conditions.
Hand scale (outstretched arm)
A rough guide to angles in the sky using your hand at arm’s length: a fist covers about 10°, three middle fingers about 5°, one finger about 1.7° and the little finger about 1°. Hands differ, so treat it as approximate.
Parameters are for guidance only and do not guarantee a sighting or non-sighting.
