1. What is Local Sidereal Time?

Local Sidereal Time (LST) is the hour angle of the vernal equinox, indicating the right ascension of stars currently on the local meridian. It's used in astronomy to point telescopes and track celestial objects.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

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

Explanation: The formula converts longitude to time (15° = 1 hour) and adds it to GST to get the sidereal time at the observer's location.

3. Importance of LST Calculation

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

4. Using the Calculator

Tips: Enter GST in hours (0-24) and longitude in degrees (-180 to +180, positive east of Greenwich). The result will be normalized to 0-24 hours.

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between sidereal and solar time?
A: Sidereal time is based on Earth's rotation relative to distant stars (23h56m per rotation), while solar time is based on the Sun (24h per rotation).

Q2: How do I get Greenwich Sidereal Time?
A: GST can be calculated from the date and UTC, or obtained from astronomical almanacs and some planetarium software.

Q3: Why divide longitude by 15?
A: Earth rotates 360° in 24 hours, so 15° of longitude equals 1 hour of time difference.

Q4: What if my longitude is west?
A: Use negative values for west longitude (e.g., -75° for New York).

Q5: How precise is this calculation?
A: This gives approximate LST. For high-precision work, consider Earth's nutation, precession, and UT1-UTC difference.