Arktische Dämmerungszeiten in Reykjavík — Twilight Calculator · FastTool

Twilight Duration at Reykjavík

At Reykjavík's latitude of 64.1°, twilight duration varies dramatically by season. At this polar location, astronomical twilight (sun −12° to −18° below horizon) typically lasts 3–6 hours or continuous during equinox periods. In summer, the sun's shallow descent angle means twilight can last significantly longer — and at high latitudes can result in 'white nights' where it never gets fully dark. This seasonal variation is what makes Reykjavík's dark-sky window so different month to month.

Reykjavik liegt direkt im Pfad der totalen Sonnenfinsternis vom 12. August 2026 — eine von nur zwei Hauptstädten (neben Nuuk, Grönland) auf der Zentrallinie. Auf 64,1°N hängt die verfinsterte Sonne um etwa 17:30 UTC tief am Himmel — eine seltene Gelegenheit, eine Sonnenfinsternis vor Islands Vulkanlandschaft unter der ewigen Sommerdämmerung zu fotografieren.

When Does It Get Truly Dark in Reykjavík?

At Reykjavík, true astronomical darkness begins when the sun drops more than 18° below the horizon — the end of astronomical twilight. At 64.1° latitude, this dark window varies from approximately 0 (white nights / midnight sun)h in summer to 16–20h in winter. During the September–March months, Reykjavík enjoys the longest dark-sky windows of the year — ideal for deep-sky astrophotography and stargazing. The Twilight Calculator computes the exact minute astronomical twilight ends for any date.

Auf 64,1°N ist Reykjavik die nördlichste Hauptstadt der Welt und erlebt von Ende Mai bis Anfang August die Mitternachtssonne, wobei die bürgerliche Dämmerung um die Juni-Sonnenwende die ganze Nacht anhält. Diese extreme Breite erzeugt die längsten sommerlichen Goldenen Stunden der Erde — bis zu 3 Stunden weiches, bernsteinfarbenes Licht, während die Sonne den Horizont entlangstreift, ohne vollständig unterzugehen.

Civil, Nautical & Astronomical Twilight Explained

Three twilight phases occur each evening and morning at Reykjavík, defined by how far the sun is below the horizon. Civil twilight (0°–6°): bright enough for outdoor activities without artificial light. Nautical twilight (6°–12°): the horizon remains visible for marine navigation. Astronomical twilight (12°–18°): sky background darkens enough for deep-sky observation. At Reykjavík's latitude, these phases progress at different speeds depending on the season — faster near the equinoxes and slower near the solstices.

Jean Meeus Algorithm & Accuracy

The Twilight Calculator for Reykjavík uses the simplified solar position algorithm from Jean Meeus's 'Astronomical Algorithms' (Chapter 25), refined with bisection iteration (15 steps) to locate each twilight threshold to sub-minute accuracy. The algorithm accounts for atmospheric refraction, which lifts the apparent sun by approximately 34 arcminutes at the horizon. Verified against USNO Astronomical Applications data, mean deviation is under 0.5 seconds for Reykjavík's coordinates.