ニューヨークの薄明時刻 — Twilight Calculator · FastTool

Twilight Duration at ニューヨーク

At ニューヨーク's latitude of 40.7°, 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 ニューヨーク's dark-sky window so different month to month.

年に2回、マンハッタンの東西の通りに人々が集まり「マンハッタンヘンジ」を目撃します——沈む太陽が行政区の格子状道路と完全に一直線になり、コンクリートの谷間に金色の輝きを投げかける瞬間です。天体物理学者ニール・ドグラース・タイソンが、1935年以来ニューヨークの宇宙への入り口であるヘイデン・プラネタリウムの館長としてこの言葉を生み出しました。

When Does It Get Truly Dark in ニューヨーク?

At ニューヨーク, true astronomical darkness begins when the sun drops more than 18° below the horizon — the end of astronomical twilight. At 40.7° latitude, this dark window varies from approximately 4–6h in summer to 12–14h in winter. During the October–March months, ニューヨーク 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40.7度に位置するニューヨークの最も長い日は、夏至に15時間5分に達します。比較すると、北緯41.9度のシカゴはさらに8分の日照を得ます——わずかな差ですが、マンハッタンヘンジのタイミングや写真家が頼りにするゴールデンアワーの時間帯にすぐに現れる違いです。

Civil, Nautical & Astronomical Twilight Explained

Three twilight phases occur each evening and morning at ニューヨーク, 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 ニューヨーク'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 ニューヨーク 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 ニューヨーク's coordinates.