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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: 05-25 (66), 05-26 (65), 05-27 (63), 05-28 (60), 05-29 (56) — by astronomy; check the weather when the night is within four days.
2025-05-25astronomy score per night — click a bar for that night2025-06-23
night ofastronomyweatheroverall best windowhighestdark hMoonMoon sep.
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°
2025-06-13 Fri 30 35 10 00:00–00:45 (marginal, 0.75 h) 50.2° 20:20 4.47 93% 107.6°
2025-06-14 Sat 30 15 5 — 50.2° 20:20 4.46 87% 120.4°
2025-06-15 Sun 29 72 21 23:10–00:35 (marginal, 1.42 h) 50.2° 20:15 4.45 79% 133.3°
2025-06-16 Mon 28 94 26 23:10–23:55 (good, 0.75 h) 50.2° 20:10 4.44 70% 146.4°
2025-06-17 Tue 26 92 24 23:10–00:00 (good, 0.83 h) 50.2° 20:05 4.43 60% 159.5°
2025-06-18 Wed 25 91 23 23:10–23:55 (good, 0.75 h) 50.2° 20:05 4.43 49% 171.7°
2025-06-19 Thu 24 90 22 23:10–23:40 (good, 0.5 h) 50.2° 20:00 4.42 37% 169.9°
2025-06-20 Fri 22 83 18 23:15–23:30 (good, 0.25 h) 50.2° 19:55 4.42 26% 156.7°
2025-06-21 Sat 20 59 12 23:15–23:55 (marginal, 0.67 h) 50.2° 19:50 4.42 17% 142.5°
2025-06-22 Sun 18 100 18 23:15–23:40 (good, 0.42 h) 50.2° 19:45 4.42 9% 127.9°
2025-06-23 Mon 17 100 17 23:15–23:35 (good, 0.33 h) 50.2° 19:45 4.43 3% 113.3°

Download: CSV · JSON


💡 API
curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2025-05-25&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.