1. What is the NWS Sunrise/Sunset Calculator?

The National Weather Service (NWS) Sunrise/Sunset Calculator provides accurate times for sunrise and sunset based on your location and date. It uses astronomical algorithms developed by the NWS.

2. How Does the Calculator Work?

The calculator uses the NWS equation:

Where:

• \( \phi \) — Latitude (degrees)
• \( \delta \) — Solar declination (degrees)
• 12 — Solar noon (adjusted for timezone)
• 1/15 — Conversion factor from degrees to hours

Explanation: The equation accounts for the Earth's axial tilt and orbital eccentricity to determine when the sun appears and disappears at your location.

3. Importance of Accurate Sunrise/Sunset Times

Details: Precise sunrise/sunset times are crucial for aviation, marine navigation, agriculture, photography, and various scientific applications.

4. Using the Calculator

Tips: Enter your latitude (-90 to 90°), longitude (-180 to 180°), and date. The more precise your coordinates, the more accurate the results.

5. Frequently Asked Questions (FAQ)

Q1: Why are my calculated times different from my local observations?
A: Times may vary due to local topography, atmospheric refraction, and the definition of sunrise/sunset (typically when the sun's upper limb appears).

Q2: How does daylight saving time affect the results?
A: The calculator provides times in UTC by default. You'll need to adjust for your local timezone and DST if applicable.

Q3: What is solar declination?
A: Solar declination is the angle between the rays of the sun and the plane of the Earth's equator, varying throughout the year.

Q4: Why does the equation include longitude adjustment?
A: Longitude affects the local solar time relative to standard time zones (15° of longitude equals 1 hour of time difference).

Q5: How accurate is this calculator?
A: Using NWS methods, it's accurate to within a minute for most locations, though local conditions may cause slight variations.