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Rozhen Observation Calendar

Which nights are best for a target over the coming weeks. The astronomy mark (darkness × altitude × Moon) is computed for every night; the weather and the overall mark exist only where Open-Meteo has a forecast (the next four days) or ERA5 history (past nights) — the rest is honestly blank.

Best nights for Great Orion Nebula: 10-15 (69), 10-02 (66), 10-03 (65), 10-01 (64), 09-30 (63) — by astronomy; check the weather when the night is within four days.
2025-09-16astronomy score per night — click a bar for that night2025-10-15
night ofastronomyweatheroverall best windowhighestdark hMoonMoon sep.
2025-09-16 Tue 29 100 29 04:10–05:30 (good, 1.33 h) 42.9° 07:10 8.44 24% 45.7°
2025-09-17 Wed 35 92 32 04:05–05:35 (good, 1.5 h) 42.9° 07:10 8.49 15% 54.8°
2025-09-18 Thu 39 100 39 03:50–05:35 (good, 1.75 h) 42.9° 07:05 8.54 8% 64.8°
2025-09-19 Fri 43 97 42 03:50–05:35 (good, 1.75 h) 42.9° 07:00 8.59 4% 75.1°
2025-09-20 Sat 45 99 45 03:45–05:35 (good, 1.83 h) 42.9° 06:55 8.64 1% 85.5°
2025-09-21 Sun 47 100 47 03:40–05:40 (good, 2.0 h) 42.9° 06:55 8.7 0% 95.9°
2025-09-22 Mon 48 100 48 03:35–05:40 (good, 2.08 h) 42.9° 06:50 8.75 1% 106.0°
2025-09-23 Tue 50 100 50 03:30–05:40 (good, 2.17 h) 42.9° 06:45 8.8 4% 115.7°
2025-09-24 Wed 52 68 35 03:30–04:00 (good, 0.5 h) 42.9° 06:40 8.85 9% 124.8°
2025-09-25 Thu 53 0 0 — 42.9° 06:35 8.9 15% 133.0°
2025-09-26 Fri 55 6 3 — 42.9° 06:35 8.95 22% 139.9°
2025-09-27 Sat 57 0 0 — 42.9° 06:30 9.0 31% 144.5°
2025-09-28 Sun 59 0 0 — 42.9° 06:25 9.05 40% 146.1°
2025-09-29 Mon 60 12 7 — 42.9° 06:20 9.09 49% 144.0°
2025-09-30 Tue 63 96 61 03:05–05:50 (good, 2.75 h) 42.9° 06:15 9.14 59% 138.7°
2025-10-01 Wed 64 0 0 — 42.9° 06:15 9.19 69% 130.9°
2025-10-02 Thu 66 0 0 — 42.9° 06:10 9.24 78% 121.6°
2025-10-03 Fri 65 0 0 — 42.9° 06:05 9.29 86% 111.0°
2025-10-04 Sat 61 100 61 03:10–05:50 (good, 2.67 h) 42.9° 06:00 9.33 93% 99.7°
2025-10-05 Sun 43 3 1 — 42.9° 05:55 9.38 98% 87.7°
2025-10-06 Mon 32 0 0 — 42.9° 05:55 9.43 100% 75.6°
2025-10-07 Tue 22 0 0 — 42.9° 05:50 9.47 99% 63.6°
2025-10-08 Wed 16 0 0 — 42.9° 05:45 9.52 95% 52.3°
2025-10-09 Thu 13 94 12 05:00–06:00 (marginal, 1.0 h) 42.9° 05:40 9.57 89% 42.6°
2025-10-10 Fri 13 10 1 — 42.9° 05:40 9.61 80% 35.9°
2025-10-11 Sat 18 4 1 — 42.9° 05:35 9.66 70% 33.9°
2025-10-12 Sun 28 52 15 02:00–04:00 (marginal, 2.0 h) 42.9° 05:30 9.7 59% 37.0°
2025-10-13 Mon 42 1 0 — 42.9° 05:25 9.74 48% 43.7°
2025-10-14 Tue 56 0 0 — 42.9° 05:20 9.79 38% 52.5°
2025-10-15 Wed 69 15 11 05:00–06:05 (marginal, 1.08 h) 42.9° 05:20 9.83 28% 62.3°

Download: CSV · JSON


💡 API
curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2025-09-16&days=30"
curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&days=30&format=csv" -o m31-calendar.csv

One row per night: score_astronomy always, score_weather / score only where a forecast or history exists (null otherwise, with weather_source saying which), best window, dark hours, Moon illumination and separation, transit. 7–60 nights. Errors: 400 with invalid_date or target_unresolved. Results are cached for six hours; calculation version 2026-10-10.1.