Dämmerungszeiten Tokio — Twilight Calculator · FastTool

Twilight Duration at Tokio

At Tokio's latitude of 35.7°, twilight duration varies dramatically by season. At this mid-latitude location, astronomical twilight (sun −12° to −18° below horizon) typically lasts 90–120 minutes 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 Tokio's dark-sky window so different month to month.

Nur 60 km westlich der Skyline Tokios bietet die Okutama-Region Bortle-3-4-Himmel, an dem die Milchstraße in klaren Nächten mit bloßem Auge sichtbar ist. Diese Nähe zu echtem Dunkelhimmel in einem der größten Ballungsräume der Welt ist äußerst selten — aktiv gefördert durch den NAOJ-Campus in Mitaka mit öffentlichen Sternbeobachtungsprogrammen.

When Does It Get Truly Dark in Tokio?

At Tokio, true astronomical darkness begins when the sun drops more than 18° below the horizon — the end of astronomical twilight. At 35.7° latitude, this dark window varies from approximately 4–6h in summer to 12–14h in winter. During the October–March months, Tokio 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.

Das Nationale Astronomische Observatorium Japans in Mitaka, Tokio, verfolgt Himmelsobjekte seit 1878 und ist damit eine der ältesten kontinuierlich betriebenen astronomischen Einrichtungen Asiens. Sein 20-cm-Refraktor entdeckte 1918 den Asteroiden 'Tokyo', und sein Sonnenturm-Teleskop überwacht noch heute täglich die Sonnenfleckenaktivität — mitten in der Metropole.

Civil, Nautical & Astronomical Twilight Explained

Three twilight phases occur each evening and morning at Tokio, 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 Tokio'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 Tokio 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 Tokio's coordinates.