Lunar Eclipse Visibility Calculator
Lunar Eclipse Visibility Calculator checks if an eclipse is visible from your latitude, longitude, and date/time for astronomical event planning.
Formulas Used in Lunar Eclipse Visibility Calculator
The calculator uses the following simplified formulas to determine visibility:
Local Sidereal Time (LST):
\\[ \text{LST} = \text{GMST} + \frac{\lambda}{15} \\]Hour Angle (HA):
\\[ \text{HA} = \text{LST} – \alpha \\]Moon Altitude:
\\[ \sin(a) = \sin(\delta) \sin(\phi) + \cos(\delta) \cos(\phi) \cos(\text{HA}) \\]Visibility Condition:
Visible if Moon altitude \\( a > 0 \\) and Sun below horizon.
Where:
- \\( \text{GMST} \\): Greenwich Mean Sidereal Time (degrees)
- \\( \lambda \\): Longitude (degrees, +E, -W)
- \\( \alpha \\): Moon’s right ascension (degrees)
- \\( \delta \\): Moon’s declination (degrees)
- \\( \phi \\): Latitude (degrees, +N, -S)
- \\( a \\): Moon’s altitude (degrees)
Example Calculations
Example 1: New York, Mar 14, 2025
Input: Latitude = 40.6768°N, Longitude = -73.9818°W, Time = 2025-03-14 06:58:45 UTC
Result: Visible, Moon Altitude ≈ 30.2° (Moon above horizon, nighttime)
Example 2: Tokyo, Sep 7, 2025
Input: Latitude = 35.6764°N, Longitude = 139.6500°E, Time = 2025-09-07 18:11:00 UTC
Result: Visible, Moon Altitude ≈ 45.8° (Moon above horizon, nighttime)
Example 3: Sydney, Mar 14, 2025
Input: Latitude = -33.8688°S, Longitude = 151.2090°E, Time = 2025-03-14 06:58:45 UTC
Result: Not Visible, Moon Altitude ≈ -10.5° (Moon below horizon)