Moon Phase on 2026-01-17
On 2026-01-17, the Moon is in the Waning Crescent phase. The visible fraction of the lunar disc illuminated by the Sun is 1.4%, with an elapsed synodic age of 28.4 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 |
|---|---|---|---|---|
Wed, Jan 14 | Waning Crescent | 17.9% | 25.4 days | View |
Thu, Jan 15 | Waning Crescent | 10.5% | 26.4 days | View |
Fri, Jan 16 | Waning Crescent | 5.0% | 27.4 days | View |
Sat, Jan 17 | Waning Crescent | 1.4% | 28.4 days | View |
Sun, Jan 18 | New Moon | 0.0% | 29.4 days | View |
Mon, Jan 19 | Waxing Crescent | 0.9% | 0.9 days | View |
Tue, Jan 20 | Waxing Crescent | 4.0% | 1.9 days | View |
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Moon Phase FAQs
Q1.What lunar phase occurs on 2026-01-17?
On 2026-01-17, the Moon is in the Waning Crescent phase, displaying approximately 1.4% disc illumination facing Earth with a lunar age of 28.4 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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