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Calcimator

Solar Eclipse Timing

Calculate solar eclipse duration and umbral shadow diameter from Moon and Sun distances. Determines eclipse type, angular sizes, and maximum totality duration.

Inputs

km
km

Results

Max Totality Duration

110.8 sec

Max Duration

1.85 min

Umbral Shadow Diameter

104.6 km

≈ 2 marathons

Eclipse Type

Annular (near-total)

Magnitude Ratio (Moon/Sun)0.9708
Moon Angular Size31.07 arcmin
Sun Angular Size32 arcmin
Angular Difference-0.94 arcmin
Max Obscuration94.2%
How to Use This Calculator
  1. Enter the Moon Distance (km) for the date of the eclipse — perigee (356,500 km) produces the longest totality, apogee (406,700 km) results in annular eclipses.
  2. Enter the Sun Distance (km) for the date — perihelion (147.1 M km) in January slightly increases totality duration.
  3. Read the Eclipse Type: total when the Moon fully covers the Sun, annular when its angular size is smaller.
  4. Check Max Totality Duration (sec) and Umbral Shadow Diameter (km) to understand the path width.
  5. Compare Moon Angular Size and Sun Angular Size (arcmin) — when the Moon's exceeds the Sun's, a total eclipse is possible.

How the result changes with Sun Distance

Sun DistanceMax Totality DurationMax DurationUmbral Shadow Diameter
147,600,000162.1 sec2.7 min153.1 km
149,100,000123.4 sec2.06 min116.6 km
150,900,00078.1 sec1.3 min73.7 km
152,400,00041.1 sec0.69 min38.8 km

What each input means

Moon Distance
Distance from Earth to Moon in km (perigee: 356,500, average: 384,400, apogee: 406,700)
Sun Distance
Distance from Earth to Sun in km (perihelion: 147.1M, average: 149.6M, aphelion: 152.1M)

How this is calculated

Formula

Duration ≈ shadow_width / shadow_speed; θ = d / D

Worked example, using the default values

  1. Identify Input Parameters
    Moon Distance = 384400, Sun Distance = 149597870 = 2 input(s) provided
  2. Calculate Max Totality Duration
    Max Totality Duration
    110.8 = 110.8
  3. Calculate Max Duration
    Max Duration
    1.85 = 1.85
  4. Calculate Umbral Shadow Diameter
    Umbral Shadow Diameter
    104.6 = 104.6
  5. Calculate Magnitude Ratio
    Magnitude Ratio
    0.9708 = 0.9708
  6. Calculate Moon Angular Size
    Moon Angular Size
    31.07 = 31.07

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