リスボンの薄明時刻 — Twilight Calculator · FastTool

Twilight Duration at リスボン

At リスボン's latitude of 38.7°, 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 リスボン's dark-sky window so different month to month.

リスボンは2026年8月12日の皆既日食の経路の南端近くに位置します。市内中心部では深い部分日食（約95%）が見られますが、北へ車で30分、カルダス・ダ・ライーニャやリオ・マイオールといった町まで行けば皆既を体験できます。象徴的な路面電車の路線で不滅のものとなった7つの丘は、三日月形の太陽がテージョ川の河口に歪んだ影を落とすのを目にするでしょう。

When Does It Get Truly Dark in リスボン?

At リスボン, true astronomical darkness begins when the sun drops more than 18° below the horizon — the end of astronomical twilight. At 38.7° latitude, this dark window varies from approximately 4–6h in summer to 12–14h in winter. During the October–March months, リスボン 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38.7度、ヨーロッパ大陸最西端に位置するリスボンは、年間2,800時間以上の日照を享受し、ヨーロッパでも最高水準です。西向きの大西洋岸に面したこの街では、海に沈む夕日が日常の儀式であり、大陸ヨーロッパ最西端のロカ岬までわずか40km、遮るもののない太陽の地平線が広がります。

Civil, Nautical & Astronomical Twilight Explained

Three twilight phases occur each evening and morning at リスボン, 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 リスボン'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 リスボン 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 リスボン's coordinates.