NOAA Solar Position Calculator

What solar azimuth means

Solar azimuth describes the Sun’s horizontal direction. Zero degrees points toward true north. Ninety degrees points east. One hundred eighty degrees points south. Two hundred seventy degrees points west. The value turns clockwise around the observer. A magnetic compass may show another direction. Local magnetic declination causes that difference.

What solar elevation means

Solar elevation measures height above the horizon. Positive values place the Sun above the astronomical horizon. Negative values place its center below that horizon. Ninety degrees means the Sun is directly overhead. Elevation changes throughout each day. It also changes across seasons and latitudes.

Geometric and apparent elevation

Geometric elevation ignores atmospheric bending. Apparent elevation includes a refraction estimate. Refraction matters most near sunrise and sunset. Dense air bends light toward the observer. The Sun can therefore appear visible while its geometric center remains below the horizon. Pressure and temperature influence the correction.

Why time zones matter

Solar equations need a precise UTC instant. Local clock time alone is insufficient. The selected time zone supplies the applicable UTC offset. IANA time zones also represent daylight-saving changes. Manual offsets remain useful for unusual cases. They should be checked carefully for historical dates.

Solar noon and clock noon

Solar noon occurs when the Sun crosses the local meridian. It rarely matches twelve o’clock exactly. Longitude within the time zone shifts solar noon. The equation of time adds a seasonal shift. Civil clock rules create another difference. Solar noon usually gives the day’s highest elevation.

Twilight stages

Civil twilight extends to six degrees below the horizon. Nautical twilight extends to twelve degrees. Astronomical twilight extends to eighteen degrees. Sky brightness depends on weather and light pollution. These thresholds still provide useful planning references. They help photographers, observers, sailors, and outdoor workers.

Shadow calculations

A vertical object casts a longer shadow when elevation is low. Shadow length equals object height divided by the tangent of elevation. The shadow points opposite the Sun’s azimuth. Below-horizon results have no direct sunlight shadow. Terrain slope can change the measured ground length.

Solar panel incidence

Panel incidence is the angle between sunlight and the panel normal. Zero degrees represents perpendicular sunlight. Larger angles reduce direct-beam exposure. A back-facing panel has a negative incidence cosine. Real energy also depends on irradiance, clouds, temperature, shading, wiring, and equipment efficiency.

Time-series analysis

A single instant answers one positioning question. A time series reveals the daily path. It supports facade studies, photography schedules, shading checks, and tracking simulations. Smaller intervals improve chart detail. Larger intervals keep long reports manageable. Exported rows support further analysis in other software.