Moon Percentage Calculator

The Moon Percentage Calculator helps users determine the percentage of the moon's surface illuminated based on the number of days since the last new moon.

Background

The moon's appearance changes in a predictable cycle called the lunar phase cycle, which lasts about 29.53 days, known as the synodic month. This calculator uses the number of days since the new moon to estimate the moon's illumination.

Calculation Formula

The formula used is:

\[ \text{Moon Percentage} = \left(\frac{\text{Days Since New Moon}}{29.53}\right) \times 100 \]

If the result is over 50%, the illumination is waning (decreasing), and the calculator adjusts accordingly.

Example Calculation

If 10 days have passed since the new moon:

\[ \text{Moon Percentage} = \left(\frac{10}{29.53}\right) \times 100 \approx 33.87\% \]

Importance and Usage

This calculator is useful for astronomers, photographers, and enthusiasts interested in the moon's phases for planning observations or understanding lunar patterns.

Common FAQs

1. What is a new moon?

   • A new moon occurs when the moon is between the Earth and the Sun, making it invisible from Earth.

2. Why is the lunar cycle not exactly 30 days?

   • The lunar cycle is about 29.53 days due to the moon's elliptical orbit and varying speed.

3. How does the moon's illumination affect tides?

   • The moon's gravitational pull influences tides, with higher tides occurring during new and full moons.