1. What is Sunset Declination?

The sunset declination (dec) is the angular distance of the Sun north or south of the celestial equator. It changes throughout the year due to Earth's axial tilt and affects the timing and position of sunset.

2. How Does the Calculator Work?

The calculator uses the declination formula:

Where:

• \( dec \) — Declination in degrees
• \( D \) — Day of the year (1-366)
• 23.45 — Earth's axial tilt in degrees

Explanation: The formula models the Sun's apparent movement north and south of the celestial equator throughout the year.

3. Importance of Declination Calculation

Details: Knowing the Sun's declination helps in predicting sunset times, solar position, and is essential for astronomy, navigation, and solar energy applications.

4. Using the Calculator

Tips: Enter the day of year (1 for January 1, 365/366 for December 31). The value must be between 1 and 366.

5. Frequently Asked Questions (FAQ)

Q1: Why does declination change?
A: Declination changes due to Earth's 23.45° axial tilt and its orbit around the Sun, creating seasonal variations.

Q2: What are typical declination values?
A: Declination ranges from +23.45° (June solstice) to -23.45° (December solstice), reaching 0° at equinoxes.

Q3: How accurate is this formula?
A: It provides a good approximation but doesn't account for small variations like Earth's elliptical orbit.

Q4: Can I use this for sunrise calculations?
A: Yes, the declination affects both sunrise and sunset positions and times.

Q5: What's the significance of day 81?
A: Day 81 (typically March 22) is approximately the spring equinox when declination is 0°.