Moon Phase on 2026-09-20
On 2026-09-20, the Moon is in the Waxing Gibbous phase. The visible fraction of the lunar disc illuminated by the Sun is 63.3%, with an elapsed synodic age of 8.6 days.
Lunar Phase & Illumination Visualizer
Jean Meeus, Astronomical Algorithms 2nd ed. Chapter 49 (Phases of the Moon)
7-Day Moon Phase Progression
| Date | Phase Name | Illumination | Moon Age | Link |
|---|---|---|---|---|
Thu, Sep 17 | Waxing Crescent | 31.9% | 5.6 days | View |
Fri, Sep 18 | First Quarter | 42.2% | 6.6 days | View |
Sat, Sep 19 | First Quarter | 52.8% | 7.6 days | View |
Sun, Sep 20 | Waxing Gibbous | 63.3% | 8.6 days | View |
Mon, Sep 21 | Waxing Gibbous | 73.2% | 9.6 days | View |
Tue, Sep 22 | Waxing Gibbous | 82.0% | 10.6 days | View |
Wed, Sep 23 | Waxing Gibbous | 89.4% | 11.6 days | View |
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Moon Phase FAQs
Q1.What lunar phase occurs on 2026-09-20?
On 2026-09-20, the Moon is in the Waxing Gibbous phase, displaying approximately 63.3% disc illumination facing Earth with a lunar age of 8.6 days since the last New Moon.
Q2.How long is a complete lunar synodic month?
A synodic month (from one New Moon to the next) averages 29.53058867 days (29 days, 12 hours, 44 minutes). This duration represents the time required for the Moon to align in the same geometric relationship relative to the Earth and Sun.
Q3.How is the illuminated fraction calculated?
Illumination is determined using Jean Meeus’ trigonometric relation k = (1 - cos(2π · phase)) / 2, where phase is the normalized progress (0.0 to 1.0) along the 29.53-day synodic cycle.
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