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Daylight Hours Formula:
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The daylight hours calculation estimates the length of daylight based on geographic latitude and solar declination. This formula helps determine how many hours of daylight a location receives on a specific day of the year.
The calculator uses the daylight hours formula:
Where:
Explanation: The formula calculates the hour angle of sunrise/sunset and converts it to hours of daylight. The factor 2/15 converts degrees to hours (15° per hour of Earth's rotation).
Details: Daylight duration affects agriculture, energy consumption, human activities, and biological rhythms. Accurate calculation helps in planning outdoor activities, solar energy systems, and understanding seasonal variations.
Tips: Enter latitude between -90° and 90° (negative for Southern Hemisphere). Solar declination ranges from -23.45° to 23.45° depending on the date. Both values must be in degrees.
Q1: What is solar declination?
A: Solar declination is the angle between the rays of the sun and the plane of the Earth's equator. It varies throughout the year due to Earth's axial tilt.
Q2: How do I find solar declination for a specific date?
A: Solar declination can be calculated using formulas or found in astronomical tables. It's approximately +23.45° on June 21, -23.45° on December 21, and 0° on equinoxes.
Q3: Why does the formula give 24 hours at high latitudes in summer?
A: When the term inside arccos is less than -1, it indicates polar day (24 hours of daylight) during summer at high latitudes near the poles.
Q4: What are typical daylight hours at the equator?
A: At the equator, daylight hours remain relatively constant at about 12 hours throughout the year, varying only slightly due to atmospheric refraction.
Q5: Can this formula be used for any date?
A: Yes, when provided with the correct solar declination for that date. The formula accounts for the geometric relationship between latitude and sun position.