1. What is the Hour Angle of the Sun?

The Hour Angle (HA) is the angular distance between the current position of the sun and its position at local solar noon. It measures how far the sun has moved from the meridian and is used in astronomy, navigation, and solar energy applications.

2. How Does the Calculator Work?

The calculator uses the Hour Angle equation:

Where:

• \( HA \) — Hour Angle (degrees)
• \( LST \) — Local Sidereal Time (hours)
• \( RA \) — Right Ascension (hours)

Explanation: The equation calculates the angular distance of the sun from the local meridian, with 15 degrees representing the Earth's rotation per hour.

3. Importance of Hour Angle Calculation

Details: Hour angle is essential for determining solar position, calculating sunrise/sunset times, designing solar tracking systems, and in celestial navigation for determining local time and position.

4. Using the Calculator

Tips: Enter Local Sidereal Time and Right Ascension in hours. Both values can be positive or negative depending on the coordinate system used.

5. Frequently Asked Questions (FAQ)

Q1: What is the range of hour angle values?
A: Hour angle typically ranges from -180° to +180°, with negative values indicating east of the meridian and positive values west of the meridian.

Q2: How is Local Sidereal Time different from Local Solar Time?
A: Local Sidereal Time is based on the position of stars, while Local Solar Time is based on the sun's position. LST advances about 4 minutes faster per day than solar time.

Q3: What does a zero hour angle indicate?
A: A zero hour angle indicates that the celestial body is on the local meridian, which corresponds to transit or culmination.

Q4: Can this calculator be used for other celestial bodies?
A: Yes, the same formula applies to any celestial object by using its specific right ascension coordinates.

Q5: Why is the conversion factor 15 degrees per hour?
A: The Earth rotates 360 degrees in 24 hours, which equals 15 degrees per hour (360 ÷ 24 = 15).