Tracing Moon's Orbit in Starlight

On the night of 13th September 2025, I set out to capture a rare celestial event as the Moon drifted past the Pleiades star cluster. Beginning at 12:30 AM and continuing until 3:20 AM, I photographed the passage continuously — from the start of the occultation until its end.

What this image reveals is not just a trail of light, but a visual record of the Moon’s orbital motion around Earth. Over the course of 1276 frames, the Moon drifted across the Pleiades. Although each frame is only a 3-second exposure, together they span 170 minutes, during which the Moon moved approximately 1.56° relative to the fixed stars — about three times its own apparent diameter.

A few calculations for the curious:

Moon’s sidereal rate ≈ 13.176°/day (≈ 0.00915°/min)

0.00915° × 170 min ≈ 1.56° total drift (≈ 93.4 arcminutes)

In lunar diameters: 1.56° ÷ 0.5° ≈ 3.11 diameters

Degrees per frame: 1.56° ÷ 1276 ≈ 0.00122°/frame

Arcseconds per frame: (1.56° × 3600) ÷ 1276 ≈ 4.39″/frame


Though invisible to the naked eye, this motion emerges when the images are aligned on the Pleiades and blended together — revealing the Moon’s graceful sweep across the starry background, faithfully tracing its orbital path.

📸 Canon 1300D + Samyang 135mm f/2 lens
📡 iOptron SkyTracker (Legacy series)

EXIF: 1276 frames · ISO 100 · f/5.6 · 3 s exposure · 135 mm
🖥️ All images manually aligned, blended, and processed in Photoshop 2023