User Rating 0.0 ★★★★★

Total Usage 1 times

Category Time

Configuration

City Preset (Search)

Target Date

Latitude

Longitude

Coordinates: 0.00, 0.00--

Sunrise--:--Azimuth: --°

Day Length--h --mvs yesterday

Sunset--:--Azimuth: --°

24-Hour Timeline

00:0006:0012:0018:0023:59

Golden Hour (AM)

--:-- → --:--

Golden Hour (PM)

--:-- → --:--

Solar Noon

--:--

Max Altitude: --°

Shadow Ratio

at Solar Noon (1m obj)

Phase	Start	End	Quality

Is this tool helpful?

Your feedback helps us improve.

★ ★ ★ ★ ★

About

This utility provides engineering-grade solar data for professionals in photography, agriculture, and logistics. Unlike basic weather apps, it computes the Astronomical, Nautical, and Civil twilight phases using high-precision trigonometric algorithms. It answers the critical question: How much usable light is available at specific coordinates on a specific date?

We define the Day Length T as the duration between the instant the upper limb of the Sun appears on the horizon and the instant it disappears, adjusted for atmospheric refraction R (≈ 34 arcminutes). The calculations utilize the Local Hour Angle LHA derived from the observer's latitude φ and solar declination δ.

Formulas

The core logic utilizes the Sunrise Equation. The hour angle ω_o is calculated as:

cosω_o = sina − sinφ ⋅ sinδcosφ ⋅ cosδ

Where a is the altitude of the sun (e.g., −0.833° for sunrise). The Shadow Length S for an object of height H is derived from the solar altitude angle α:

S = H × cot(α)

Reference Data

Solar Phase	Sun Angle θ	Lux lx	Utility Case
Solar Noon	MAX	100,000	Maximum PV energy generation. Shortest shadows.
Golden Hour	6° to −4°	500	Cinematography, landscape photography (warm tones).
Civil Twilight	−0.83° to −6°	300	Construction work ends. Streetlights activate.
Blue Hour	−4° to −8°	10	Cityscape photography (cool tones).
Nautical Twilight	−6° to −12°	1	Horizon visible at sea. Navigation possible.
Astronomical Twilight	−12° to −18°	0.001	Deep sky observation begins. Faint stars visible.

Frequently Asked Questions

Weather apps often simplify calculations by using a central coordinate for a city (e.g., the city hall). This tool uses the exact latitude and longitude you provide or select. A difference of just 10 kilometers East/West can shift times by minutes. Furthermore, we account for standard atmospheric refraction, which some simplified apps ignore.

The Shadow Ratio indicates how long a shadow is compared to the object's height at Solar Noon. A ratio of 0.5 means a 10-meter pole casts a 5-meter shadow. Photographers use this to determine contrast depth; architects use it for overhang planning.

Yes. The math handles negative latitudes (South) and longitudes (West) correctly. Users in Australia or South America will see correct seasonal inversions (e.g., longest days in December).

In polar regions, the sun may not set (Polar Day) or not rise (Polar Night). The tool detects these states when the cosine of the hour angle falls outside the domain [-1, 1] and displays "24h Daylight" or "24h Darkness" accordingly.