Peaks of Eternal Light: Lunar Polar Solar Siting (2D)

Sun Geometry

Base sun elevation 1.4°

Seasonal wobble (±) 1.0°

Day speed 1.0×

Candidate threshold 80%

Click any cell on the top-down map to select it as a candidate outpost site. The strip below shows the exact ray the engine casts from that site toward the current sun bearing.

Selected Site

Sun margin now

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Status

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Year-round illumination (worst season)

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Peak-of-eternal-light candidates on rim

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How it works

Near the lunar poles the Moon's tiny ~1.5° axial tilt keeps the Sun perpetually near the horizon — it never rises high, and it circles the sky once per lunar day (≈29.5 Earth days) instead of rising and setting like on Earth. Whether a point is lit therefore depends almost entirely on local topography, not time of day:

horizon(θ) = max angle to the terrain skyline
             looking toward azimuth θ from this point
lit(θ) ⇔ sun_elevation > horizon(θ)

This engine ray-marches the same crater-rim heightfield used by the 3D version, but casts every ray flat in the ground plane and draws the result two ways: a top-down grid coloured by that horizon test, and a live geometric cross-section — the actual terrain profile the selected site looks toward, unrolled along the current sun bearing — with the sun's ray drawn against it at its true grazing angle.

A site's year-round illumination sweeps all 360° of azimuth at the worst-case elevation (base − seasonal wobble, the sun's lowest yearly excursion) and reports the fraction of directions still unblocked. Rim points that stay above the candidate threshold through that whole worst-case sweep are the real-world "peaks of eternal light" — the sites NASA and ESA have studied for continuous solar power at a permanent lunar outpost, avoiding the two-week battery-draining lunar night that grounds a base sited on the floor.

Base sun elevation — the Sun's mean height above the local horizon at this latitude.
Seasonal wobble — how far axial tilt swings that elevation down at the worst point in the Moon's orbit; a wider wobble shrinks the eternal-light set.
View toggle — instant shadow map (current moment) vs. year-round candidate heatmap (worst-case sweep).
Cross-section strip — the real terrain profile from the selected site outward along the current sun bearing; the dotted line marks the horizon angle the sun must clear.

Top-down rim map

Sunlit now In shadow Selected site

Cross-section toward the sun