1. What is Local Sidereal Time?

Local Sidereal Time (LST) is the hour angle of the vernal equinox at a specific location. It represents the right ascension of celestial objects currently on the observer's meridian and is used in astronomical observations and telescope pointing.

2. How Does the Calculator Work?

The calculator uses the LST formula:

Where:

• \( GST \) — Greenwich Sidereal Time in hours
• \( Longitude \) — Observer's longitude in degrees (positive east, negative west)

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

3. Importance of LST Calculation

Details: LST is essential for astronomical observations as it helps determine which celestial objects are visible at a given time and location. It's also used in telescope control systems and satellite tracking.

4. Using the Calculator

Tips: Enter GST in hours (0-24) and longitude in degrees (-180 to +180, positive for east, negative for west). The result will be normalized to the 0-24 hour range.

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between sidereal time 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 rotation relative to the Sun (24h per rotation).

Q2: How do I get Greenwich Sidereal Time?
A: GST can be calculated from the Julian date or obtained from astronomical almanacs and some astronomy software/apps.

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 LST result is negative or >24?
A: The calculator automatically normalizes results to the 0-24 hour range by adding or subtracting 24 as needed.

Q5: How precise is this calculation?
A: The calculation is mathematically precise, but actual observing conditions may require additional corrections for atmospheric refraction and other factors.