パリの薄明時刻 — Twilight Calculator · FastTool

Twilight Duration at パリ

At パリ's latitude of 48.9°, twilight duration varies dramatically by season. At this high-latitude location, astronomical twilight (sun −12° to −18° below horizon) typically lasts 2–4 hours 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 パリ's dark-sky window so different month to month.

1667年にルイ14世の命で設立されたパリ天文台は、世界最古の継続的に運用されている天文台です。アラゴ・メダリオン——パリの歩道に埋め込まれた135個の青銅製ディスク——は、1884年に国際子午線会議がロンドンに標準化することを決議するまで、グリニッジと世界の本初子午線の地位を競ったパリ子午線を今も示しています。

When Does It Get Truly Dark in パリ?

At パリ, true astronomical darkness begins when the sun drops more than 18° below the horizon — the end of astronomical twilight. At 48.9° latitude, this dark window varies from approximately 0–3 (white nights possible)h in summer to 14–16h in winter. During the September–April months, パリ 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48.9度のパリでは、夏の日が16時間10分まで延びます——より低い中緯度のニューヨークや東京の15時間の最大値よりかなり長くなります。この延長された夏の日照は、パリの名高い8月の澄んだ空と相まって、ヨーロッパの主要首都の中でも最も長く最も写真映えするゴールデンアワーの時間帯を生み出します。

Civil, Nautical & Astronomical Twilight Explained

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