ソウルの薄明時刻 — Twilight Calculator · FastTool

Twilight Duration at ソウル

At ソウル's latitude of 37.6°, 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 ソウル's dark-sky window so different month to month.

ソウルの果川（クァチョン）国立科学館は、韓国最大の公共天文台を運営しており、1メートル反射望遠鏡と専用の太陽観測デッキを備えています。近隣の大田（テジョン）にある韓国天文研究院（KASI）はGMT（巨大マゼラン望遠鏡）計画への主要な貢献機関であり、ソウルのアマチュア天文クラブは50以上を数えます——アジアで最も密度の高い地域の一つです。

When Does It Get Truly Dark in ソウル?

At ソウル, true astronomical darkness begins when the sun drops more than 18° below the horizon — the end of astronomical twilight. At 37.6° latitude, this dark window varies from approximately 4–6h in summer to 12–14h in winter. During the October–March months, ソウル 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.

北緯37.6度のソウルでは、湿潤大陸性気候の下で真夏の日照は14時間45分に達します。1月の夜の−5°Cから7月の昼の30°Cまでの劇的な季節差は、超モダンなスカイラインと山に囲まれた自然の盆地というソウルの印象的な対比と呼応し、太陽の通り道は東の北漢山から西の冠岳山まで正確な弧を描きます。

Civil, Nautical & Astronomical Twilight Explained

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