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Last Quarter55.3% Illumination

Moon Phase on 2026-10-03

On 2026-10-03, the Moon is in the Last Quarter phase. The visible fraction of the lunar disc illuminated by the Sun is 55.3%, with an elapsed synodic age of 21.6 days.

Lunar Phase & Illumination Visualizer

Jean Meeus, Astronomical Algorithms 2nd ed. Chapter 49 (Phases of the Moon)

FormulaIllumination = (1 - cos(2π · Phase)) / 2
Select Date:
77% Cycle
Last Quarter
44.1% Illuminated
Visible fraction of the lunar disc facing Earth
0% (New)50% (Quarter)100% (Full)
Moon Age22.7 daysin 29.53d synodic cycle
Phase Angle (k)276.8°geometric elongation
Astronomical Algorithm Note: Moon phases are governed by the synodic month (mean length: 29.53058867 days). Phase zero corresponds to the conjunction of the Moon and Sun (New Moon), while phase 0.50 denotes the exact opposition (Full Moon).

7-Day Moon Phase Progression

DatePhase NameIlluminationMoon AgeLink
Wed, Sep 30
Waning Gibbous83.9%18.6 daysView
Thu, Oct 1
Waning Gibbous75.4%19.6 daysView
Fri, Oct 2
Waning Gibbous65.7%20.6 daysView
Sat, Oct 3
Last Quarter55.3%21.6 daysView
Sun, Oct 4
Last Quarter44.7%22.6 daysView
Mon, Oct 5
Waning Crescent34.3%23.6 daysView
Tue, Oct 6
Waning Crescent24.7%24.6 daysView

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Moon Phase FAQs

Q1.What lunar phase occurs on 2026-10-03?

On 2026-10-03, the Moon is in the Last Quarter phase, displaying approximately 55.3% disc illumination facing Earth with a lunar age of 21.6 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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