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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: 03-15 (40), 03-16 (38), 03-17 (38), 03-18 (36), 03-19 (34) — by astronomy; check the weather when the night is within four days.
2031-03-15astronomy score per night — click a bar for that night2031-04-13
night ofastronomyweatheroverall best windowhighestdark hMoonMoon sep.
2031-03-15 Sat 40 — unknown 20:05–21:45 (good, 1.67 h) 42.9° 18:25 8.99 54% 153.0°
2031-03-16 Sun 38 — unknown 20:05–21:40 (good, 1.58 h) 42.9° 18:20 8.94 42% 151.9°
2031-03-17 Mon 38 — unknown 20:05–21:35 (good, 1.5 h) 42.9° 18:20 8.89 31% 145.0°
2031-03-18 Tue 36 — unknown 20:05–21:35 (good, 1.5 h) 42.9° 18:15 8.84 21% 134.9°
2031-03-19 Wed 34 — unknown 20:05–21:30 (good, 1.42 h) 42.9° 18:10 8.78 13% 123.4°
2031-03-20 Thu 32 — unknown 20:10–21:25 (good, 1.25 h) 42.9° 18:05 8.73 6% 111.2°
2031-03-21 Fri 30 — unknown 20:10–21:20 (good, 1.17 h) 42.9° 18:00 8.68 2% 98.9°
2031-03-22 Sat 29 — unknown 20:10–21:15 (good, 1.08 h) 42.9° 18:00 8.63 0% 86.6°
2031-03-23 Sun 28 — unknown 20:10–21:15 (good, 1.08 h) 42.9° 17:55 8.58 1% 74.7°
2031-03-24 Mon 25 — unknown 20:15–21:10 (good, 0.92 h) 42.9° 17:50 8.52 4% 63.1°
2031-03-25 Tue 22 — unknown 20:15–21:05 (good, 0.83 h) 42.9° 17:45 8.47 8% 52.2°
2031-03-26 Wed 19 — unknown 20:15–20:55 (good, 0.67 h) 42.9° 17:40 8.42 15% 42.3°
2031-03-27 Thu 16 — unknown 20:20–20:45 (good, 0.42 h) 42.9° 17:40 8.36 22% 34.0°
2031-03-28 Fri 12 — unknown 20:20–20:30 (good, 0.17 h) 42.9° 17:35 8.31 31% 28.2°
2031-03-29 Sat 9 — unknown 20:20–21:20 (marginal, 1.0 h) 42.9° 17:30 8.26 40% 26.6°
2031-03-30 Sun 6 — unknown 21:20–22:10 (marginal, 0.83 h) 42.9° 18:25 8.2 49% 29.6°
2031-03-31 Mon 4 — unknown 21:25–21:55 (marginal, 0.5 h) 42.9° 18:25 8.15 59% 36.2°
2031-04-01 Tue 4 — unknown 21:25–21:50 (marginal, 0.42 h) 42.9° 18:20 8.09 68% 44.8°
2031-04-02 Wed 3 — unknown 21:25–21:45 (marginal, 0.33 h) 42.9° 18:15 8.04 76% 54.7°
2031-04-03 Thu 3 — unknown 21:25–21:45 (marginal, 0.33 h) 42.9° 18:10 7.98 84% 65.3°
2031-04-04 Fri 3 — unknown 21:30–21:45 (marginal, 0.25 h) 42.9° 18:05 7.93 91% 76.5°
2031-04-05 Sat 3 — unknown 21:30–21:50 (marginal, 0.33 h) 42.9° 18:05 7.87 96% 88.1°
2031-04-06 Sun 3 — unknown 21:30–21:50 (marginal, 0.33 h) 42.9° 18:00 7.82 99% 100.1°
2031-04-07 Mon 3 — unknown 21:35–21:45 (marginal, 0.17 h) 42.9° 17:55 7.76 100% 112.3°
2031-04-08 Tue 2 — unknown 21:00–21:10 (marginal, 0.17 h) 42.9° 17:50 7.7 98% 124.4°
2031-04-09 Wed 2 — unknown 21:00–21:05 (marginal, 0.08 h) 42.9° 17:45 7.65 94% 135.8°
2031-04-10 Thu 2 — unknown — 42.9° 17:45 7.59 87% 145.9°
2031-04-11 Fri 1 — unknown — 42.9° 17:40 7.53 78% 152.4°
2031-04-12 Sat 1 — unknown — 42.9° 17:35 7.48 68% 152.9°
2031-04-13 Sun 1 — unknown — 42.9° 17:30 7.42 57% 147.1°

Download: CSV · JSON


💡 API
curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2031-03-15&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.