ア・コルーニャの薄明時刻 — Twilight Calculator · FastTool

Twilight Duration at ア・コルーニャ

At ア・コルーニャ's latitude of 43.4°, 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 ア・コルーニャ's dark-sky window so different month to month.

ア・コルーニャは2026年8月12日の皆既日食の中心線上に位置し、経路上の主要都市で最長の皆既時間（1分58秒）を誇ります。1世紀に建てられたローマ時代の灯台でユネスコ世界遺産のヘラクレスの塔は、約2000年にわたりこの大西洋岸を見守ってきましたが、月の影がビスケー湾を横切るのを目撃することになります。

When Does It Get Truly Dark in ア・コルーニャ?

At ア・コルーニャ, true astronomical darkness begins when the sun drops more than 18° below the horizon — the end of astronomical twilight. At 43.4° latitude, this dark window varies from approximately 4–6h in summer to 12–14h in winter. During the October–March months, ア・コルーニャ 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43.4度、スペイン北西部の大西洋岸に位置するア・コルーニャの太陽の軌道は、カンタブリア海によって形作られています。夏の日没は午後10時を過ぎても海の上に残り、ヨーロッパ最長（13km超）の海辺の遊歩道パセオ・マリティモのガラス張りのファサードに写真家たちを惹きつける、延長されたゴールデンアワーを生み出します。

Civil, Nautical & Astronomical Twilight Explained

Three twilight phases occur each evening and morning at ア・コルーニャ, 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 ア・コルーニャ'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 ア・コルーニャ 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 ア・コルーニャ's coordinates.