Fajr and Isha Angles: 15, 18 and 19.5 Degrees Explained

A Fajr or Isha angle is the depth of the sun below the horizon, in degrees, that a timetable uses to mark dawn or the end of evening twilight. A 15° angle gives a later Fajr and an earlier Isha than 18°, and 19.5° gives an earlier Fajr still. The gap between 15° and 18° is about 12 to 15 minutes near the equator and grows with latitude: on 21 December 2026 it is 21 minutes in London. In summer at high latitudes, the deeper angles may not be reached at all.

Key Takeaways

• Astronomers divide twilight into civil (6°), nautical (12°) and astronomical (18°) stages. Prayer timetables borrow the same measure: the sun's depth below the horizon.
• Published methods use Fajr angles from 15° (ISNA) through 18° (Muslim World League, Karachi) to 19.5° (Egypt) and 20° (Singapore).
• Each extra degree adds about 4 minutes near the equator and 7 or more at higher latitudes, so the spread between methods is widest far from the equator.
• Above about 48.6°N, the sun stays less than 18° below the horizon for weeks around the June solstice, and a fallback rule decides the times.

What the twilight angles measure

Twilight is the light in the sky while the sun is below the horizon. The US Naval Observatory's page on rise, set and twilight definitions sets three stages by the position of the sun's centre: civil twilight at 6° below the horizon, nautical twilight at 12°, and astronomical twilight at 18°. Beyond 18°, the page explains, scattered sunlight is fainter than starlight and other natural sources, so the sky is fully dark.

Prayer times use the same measure for a different purpose. The religious texts describe events in the sky, not angles. In Sahih Muslim 612a, the Prophet ﷺ says the time of Maghrib lasts "until the twilight has disappeared", and the time of Fajr lasts until the first part of the sun appears. The Quran (2:187) allows eating and drinking in the nights of Ramadan "until the white thread of dawn becomes distinct to you from the black thread [of night]" (Sahih International translation of the meaning, quran.com 2:187).

An astronomical calculation cannot see the sky, so it uses a proxy. A timetable picks a solar depression angle that is meant to match the moment true dawn appears in the east, or the moment the evening glow is gone from the west. Fajr is then the time the sun rises to that angle; Isha is the time it sinks to it.

True dawn and false dawn

The texts distinguish two kinds of early light. In Sahih Muslim 1094a, the Prophet ﷺ tells people that a vertical streak of whiteness should not stop them from eating before the fast; the dawn that begins the fast is the light that spreads along the horizon. The earlier vertical light is often called the false dawn. The angle debate is about when the second, horizontal light first becomes visible.

Red and white evening twilight

Isha has its own question: which glow has to disappear. The documentation of the open-source adhan prayer-time library summarises the two readings of shafaq: the red glow (used by the Shafi'i, Maliki and Hanbali schools, generally giving an earlier Isha) and the white glow (used by the Hanafi school, giving a later Isha). The white glow lasts longer, which is one reason some methods use the same angle for Isha as for Fajr and others use a smaller Isha angle.

Which authorities use which angles

Each calculation method is a pair of numbers, or a number and a fixed interval. The table lists the parameters as the adhan library implements them in its METHODS reference and its source code (version 4.4.3). Official timetables can add their own minute offsets, so treat these as the core angles rather than a copy of any published timetable.

Three groups stand out. The 18° methods sit exactly on astronomical twilight. The 15° method of ISNA is shallower and gives the latest Fajr. The Egyptian 19.5° and Singapore 20° angles are deeper than astronomical twilight and give the earliest Fajr. The Umm al-Qura and Qatar methods sidestep the Isha angle entirely with a fixed interval. For a broader side-by-side of every method, see prayer time calculation methods compared.

What observations of dawn have found

Field studies do not settle on one number. They depend on the site, the sky and whether the observer uses the eye or a camera.

• A camera study published in Sains Malaysiana in 2018 recorded 64 days of dawn at sites in Malaysia and Indonesia between 2° and 7° N. The first visible dawn came at depressions between 14.5° and 18.5°, with a mean of 16.67°, and the authors proposed 17° for the dawn prayer.
• Naked-eye observations at Tobruk in Libya, published in Al-Hilal: Journal of Islamic Astronomy in 2021 by researchers from Egypt's National Research Institute of Astronomy and Geophysics, estimated the start of morning twilight at about 13.5°, falling to about 11.5° in poor visibility.

These results are why the angle remains debated. Whether a timetable should follow a precautionary deeper angle or an observed shallower one is a question for scholars, and communities follow the method their mosque or national authority adopts.

How many minutes the angle changes

The same angle produces different clock times in different places, because the sun crosses the horizon steeply near the equator and at a shallow slant at high latitudes. The table shows how long before sunrise Fajr falls at each angle.

Times were calculated with the open-source adhan library (version 4.4.3) using custom parameters with equal Fajr and Isha angles, for each city's centre coordinates and local time zone. Isha after sunset shows almost the same gaps on the same dates; in New York on 21 June 2026, for example, Isha is 100 minutes after sunset at 15° and 126 minutes at 18°.

A worked example makes the effect concrete. On Sunday 21 June 2026 (6 Muharram 1448) in New York, sunrise is at 05:25. Fajr is at 03:45 with 15°, 03:19 with 18° and 03:04 with 19.5°. In Kuala Lumpur on the same date, the same three angles give 06:04, 05:50 and 05:44. The method choice moves Fajr by 41 minutes in New York but only 20 minutes in Kuala Lumpur.

Two patterns show in the numbers. The gap grows with latitude, and at mid-latitudes it is wider in summer than at the equinox. Near the equator the season barely matters.

When the sun never reaches the angle

At high latitudes in summer, the sun can stay so close to the horizon that it never sinks 18° below it. At solar midnight the sun's depression equals 90° minus the latitude minus the sun's declination. Around the June solstice the declination is about 23.4° north, so the sun fails to reach 18° anywhere north of about 48.6°N, 15° north of about 51.6°N, and 19.5° north of about 47.1°N.

That puts Paris (48.9°N) and London (51.5°N) inside the zone for the deeper angles. Checking each night of 2026 with adhan, the sun does not get 18° below London's horizon for about 60 nights, from roughly 23 May to 21 July. A 15° angle is still reached in London on the solstice, but only just: on 21 June 2026 the calculation puts 15° Isha at 00:49 and 15° Fajr at 01:15, 26 minutes later. In Edinburgh (56.0°N), even 15° is missing for about 73 nights.

When the angle does not occur, a timetable has to use a fallback rule instead of astronomy. The adhan library offers three: Fajr no earlier than the middle of the night, a one-seventh-of-the-night rule, and a portion of the night scaled from the angle. Its default is the middle of the night, which put both 18° Fajr and 18° Isha in London at 01:02 on 21 June 2026. Which rule to follow is a religious decision as much as a technical one. How to set it up in a prayer app is covered on our sister site Everyday Muslim in prayer time settings for long summer days.

Common questions

Is 18° the "correct" angle?

Astronomically, 18° is the point at which the sky is fully dark. Whether Fajr begins there, or at a shallower depression when the spreading light becomes visible, is where scholars and observers differ. Follow the method your local mosque or national authority uses, and ask a qualified scholar if you need to choose.

Why is Isha sometimes a fixed number of minutes after Maghrib?

The Umm al-Qura and Qatar methods set Isha 90 minutes after sunset instead of using an angle. In Makkah on 20 March 2026 (1 Shawwal 1447), that puts Isha 16 minutes later than an 18° angle would (74 minutes after sunset) and 10 minutes later than 19.5° (80 minutes). Far from Arabia, a fixed interval and an angle can drift much further apart.

Does the angle affect Maghrib or sunrise?

Mostly not. Sunrise and Maghrib are tied to the sun's upper edge crossing the horizon, so they match across the methods listed here, apart from small minute offsets some methods add. The Tehran method is the exception: adhan sets its Maghrib at a 4.5° depression. Only Fajr and Isha depend on the twilight angle. The full sequence of the five times is explained in how prayer times are calculated.

Check the angle behind your timetable

Find out which method your mosque's printed timetable uses, then compare it with a calculated one. The daily prayer times page shows each prayer for your location, and the monthly timetable lets you watch how far Fajr and Isha move across the season. If your city is north of about 48°N, also ask your mosque which high-latitude rule it follows in summer, since that choice, not the angle, sets Fajr and Isha around the June solstice.