diff --git a/test_last_full_moon.py b/test_last_full_moon.py
new file mode 100644
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+++ b/test_last_full_moon.py
@@ -0,0 +1,66 @@
+#!/usr/bin/env python3
+"""test_last_full_moon.py — smoke-test moon_phase.py against the most recent full moon.
+
+Exercises:
+  - full_moons_in_range()        — phase detection
+  - sun_events_in_range()        — sunrise/sunset almanac (requires bare topos, not earth+topos)
+  - illumination() / altaz() / parallactic_angle()
+
+Run from the sky-cam directory:
+
+  python3 test_last_full_moon.py
+"""
+
+import sys
+import pathlib
+from datetime import datetime, timedelta, timezone
+
+HERE = pathlib.Path(__file__).resolve().parent
+sys.path.insert(0, str(HERE))
+
+import moon_phase as mp
+
+
+def main() -> int:
+    now = datetime.now(timezone.utc)
+
+    # Last full moon: search back up to 35 days
+    candidates = mp.full_moons_in_range(now - timedelta(days=35), now)
+    if not candidates:
+        print("ERROR: no full moon found in the last 35 days", file=sys.stderr)
+        return 1
+    fm = candidates[-1]
+
+    print(f"last full moon (UTC) : {fm.strftime('%Y-%m-%dT%H:%M:%SZ')}")
+    print(f"local                : {mp._format_local(fm)}")
+
+    # Moon stats at exact full moon moment
+    illum = mp.illumination(fm)
+    pa = mp.phase_angle(fm)
+    alt, az = mp.altaz(fm)
+    para = mp.parallactic_angle(fm)
+    print(f"illumination         : {illum:.4f}  ({illum*100:.1f}%)")
+    print(f"phase angle          : {pa:.2f}°  (0° = full)")
+    print(f"altitude / azimuth   : {alt:.2f}° / {az:.2f}°")
+    print(f"parallactic angle    : {para:.2f}°")
+    print()
+
+    # Sunrise/sunset for the 24-hour window around the full moon — exercises the fix
+    day_start = fm.replace(hour=0, minute=0, second=0, microsecond=0)
+    day_end = day_start + timedelta(days=1)
+    events = mp.sun_events_in_range(day_start, day_end)
+    if events:
+        print(f"sun events on {day_start.strftime('%Y-%m-%d')} (UTC):")
+        for t, is_rise in events:
+            label = "sunrise" if is_rise else "sunset "
+            print(f"  {label} {t.strftime('%H:%M:%S')} UTC  ({mp._format_local(t)})")
+    else:
+        print(f"no sun events found on {day_start.strftime('%Y-%m-%d')} (polar location?)")
+
+    print()
+    print("OK")
+    return 0
+
+
+if __name__ == "__main__":
+    sys.exit(main())