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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 3C 273: 05-17 (83), 05-16 (81), 05-18 (81), 05-19 (79), 05-20 (77) — by astronomy; check the weather when the night is within four days.
2025-05-14astronomy score per night — click a bar for that night2025-06-12
night ofastronomyweatheroverall best windowhighestdark hMoonMoon sep.
2025-05-14 Wed 71 88 63 23:00–01:00 (good, 2.0 h) 50.2° 22:20 5.62 95% 73.6°
2025-05-15 Thu 76 0 0 — 50.2° 22:15 5.56 90% 85.8°
2025-05-16 Fri 81 0 0 — 50.2° 22:10 5.51 84% 98.1°
2025-05-17 Sat 83 30 25 00:00–00:50 (good, 0.83 h) 50.2° 22:10 5.46 76% 110.6°
2025-05-18 Sun 81 100 81 22:40–01:55 (good, 3.25 h) 50.2° 22:05 5.41 66% 123.3°
2025-05-19 Mon 79 92 72 22:40–01:50 (good, 3.17 h) 50.2° 22:00 5.36 56% 136.3°
2025-05-20 Tue 77 43 33 22:40–00:00 (good, 1.33 h) 50.2° 21:55 5.31 45% 149.5°
2025-05-21 Wed 76 68 52 23:00–01:45 (good, 2.75 h) 50.2° 21:55 5.26 34% 162.9°
2025-05-22 Thu 73 96 70 22:45–01:35 (good, 2.83 h) 50.2° 21:50 5.21 24% 174.0°
2025-05-23 Fri 71 6 4 — 50.2° 21:45 5.16 15% 166.1°
2025-05-24 Sat 69 0 0 — 50.2° 21:40 5.12 7% 151.9°
2025-05-25 Sun 66 0 0 — 50.2° 21:35 5.07 2% 137.0°
2025-05-26 Mon 65 79 51 22:50–01:00 (good, 2.17 h) 50.2° 21:35 5.03 0% 122.1°
2025-05-27 Tue 63 99 63 22:50–01:20 (good, 2.5 h) 50.2° 21:30 4.98 1% 107.2°
2025-05-28 Wed 60 94 56 22:55–01:10 (good, 2.25 h) 50.2° 21:25 4.94 5% 92.6°
2025-05-29 Thu 56 41 23 22:55–01:00 (marginal, 2.08 h) 50.2° 21:20 4.9 11% 78.3°
2025-05-30 Fri 51 0 0 — 50.2° 21:15 4.86 19% 64.5°
2025-05-31 Sat 44 86 38 22:55–00:10 (good, 1.25 h) 50.2° 21:15 4.82 28% 51.2°
2025-06-01 Sun 34 65 22 22:10–00:45 (marginal, 2.58 h) 50.2° 21:10 4.79 38% 38.4°
2025-06-02 Mon 26 94 24 00:00–00:30 (good, 0.5 h) 50.2° 21:05 4.75 48% 26.0°
2025-06-03 Tue 21 100 21 23:00–01:20 (marginal, 2.33 h) 50.2° 21:00 4.72 58% 14.3°
2025-06-04 Wed 17 100 17 23:00–01:10 (marginal, 2.17 h) 50.2° 21:00 4.69 67% 5.9°
2025-06-05 Thu 13 0 0 — 50.2° 20:55 4.65 76% 12.3°
2025-06-06 Fri 11 99 11 23:05–00:50 (marginal, 1.75 h) 50.2° 20:50 4.63 83% 23.4°
2025-06-07 Sat 10 100 10 23:05–00:40 (marginal, 1.58 h) 50.2° 20:45 4.6 90% 34.9°
2025-06-08 Sun 12 97 12 23:05–00:40 (marginal, 1.58 h) 50.2° 20:40 4.57 95% 46.7°
2025-06-09 Mon 14 85 12 23:05–00:40 (marginal, 1.58 h) 50.2° 20:40 4.55 98% 58.5°
2025-06-10 Tue 17 29 5 00:00–00:45 (marginal, 0.75 h) 50.2° 20:35 4.53 100% 70.5°
2025-06-11 Wed 20 100 20 23:10–23:45 (good, 0.58 h) 50.2° 20:30 4.51 100% 82.7°
2025-06-12 Thu 23 98 23 23:10–00:00 (good, 0.83 h) 50.2° 20:25 4.49 97% 95.1°

Download: CSV · JSON


💡 API
curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2025-05-14&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.