1. What is Sidereal Time?

Sidereal time is a timekeeping system that astronomers use to locate celestial objects. It is based on Earth's rotation relative to distant stars rather than the Sun.

2. How Does the Calculator Work?

The calculator uses the sidereal time formula:

Where:

• \( LST \) — Local Sidereal Time (hours)
• \( GST \) — Greenwich Sidereal Time (hours)
• \( longitude \) — Observer's longitude (degrees, positive east of Greenwich)

Explanation: The formula converts longitude to time (15° = 1 hour) and adds it to GST to get local sidereal time.

3. Importance of Sidereal Time

Details: Sidereal time is essential for telescope pointing, astronomical observations, and satellite tracking. It helps determine which celestial objects are visible at a given time and location.

4. Using the Calculator

Tips: Enter GST in hours and longitude in degrees (positive for east, negative for west). The result will be in hours (0-24).

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between sidereal and solar time?
A: A sidereal day is about 4 minutes shorter than a solar day because Earth moves in its orbit around the Sun.

Q2: How do I get Greenwich Sidereal Time?
A: GST can be calculated from the date and time using astronomical algorithms or obtained from astronomical almanacs.

Q3: Why divide longitude by 15?
A: Earth rotates 15 degrees per hour, so dividing longitude by 15 converts degrees to hours.

Q4: What if my LST result is negative or >24?
A: The calculator automatically normalizes the result to the 0-24 hour range.

Q5: How precise is this calculation?
A: For most amateur astronomy purposes, this calculation is sufficiently precise.