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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 (37), 03-16 (32), 03-17 (27), 03-18 (21), 03-19 (16) — by astronomy; check the weather when the night is within four days.
2040-03-15astronomy score per night — click a bar for that night2040-04-13
night ofastronomyweatheroverall best windowhighestdark hMoonMoon sep.
2040-03-15 Thu 37 — unknown 20:05–21:40 (good, 1.58 h) 42.9° 18:25 8.95 10% 55.1°
2040-03-16 Fri 32 — unknown 20:05–21:30 (good, 1.42 h) 42.9° 18:20 8.9 16% 45.4°
2040-03-17 Sat 27 — unknown 20:05–21:20 (good, 1.25 h) 42.9° 18:15 8.84 24% 37.3°
2040-03-18 Sun 21 — unknown 20:05–21:05 (good, 1.0 h) 42.9° 18:10 8.79 33% 31.8°
2040-03-19 Mon 16 — unknown 20:10–21:55 (marginal, 1.75 h) 42.9° 18:05 8.74 42% 30.0°
2040-03-20 Tue 12 — unknown 20:10–21:45 (marginal, 1.58 h) 42.9° 18:05 8.69 52% 32.4°
2040-03-21 Wed 9 — unknown 20:10–21:30 (marginal, 1.33 h) 42.9° 18:00 8.64 61% 38.1°
2040-03-22 Thu 8 — unknown 20:10–21:20 (marginal, 1.17 h) 42.9° 17:55 8.59 70% 45.9°
2040-03-23 Fri 7 — unknown 20:15–21:15 (marginal, 1.0 h) 42.9° 17:50 8.53 78% 55.0°
2040-03-24 Sat 8 — unknown 20:15–21:15 (marginal, 1.0 h) 42.9° 17:45 8.48 86% 64.9°
2040-03-25 Sun 9 — unknown 21:15–22:15 (marginal, 1.0 h) 42.9° 18:45 8.43 92% 75.5°
2040-03-26 Mon 10 — unknown 21:15–22:20 (marginal, 1.08 h) 42.9° 18:40 8.37 97% 86.4°
2040-03-27 Tue 11 — unknown 21:20–21:25 (good, 0.08 h) 42.9° 18:35 8.32 99% 97.7°
2040-03-28 Wed 12 — unknown 21:20–21:30 (good, 0.17 h) 42.9° 18:30 8.27 100% 109.1°
2040-03-29 Thu 14 — unknown 21:20–21:35 (good, 0.25 h) 42.9° 18:30 8.21 98% 120.4°
2040-03-30 Fri 13 — unknown 21:25–21:45 (good, 0.33 h) 42.9° 18:25 8.16 94% 131.2°
2040-03-31 Sat 12 — unknown 21:25–21:40 (good, 0.25 h) 42.9° 18:20 8.1 87% 140.8°
2040-04-01 Sun 10 — unknown 21:25–21:35 (good, 0.17 h) 42.9° 18:15 8.05 79% 147.7°
2040-04-02 Mon 9 — unknown 21:25–21:30 (good, 0.08 h) 42.9° 18:10 7.99 68% 149.8°
2040-04-03 Tue 7 — unknown 21:30–22:00 (marginal, 0.5 h) 42.9° 18:10 7.94 57% 146.2°
2040-04-04 Wed 6 — unknown 21:30–21:55 (marginal, 0.42 h) 42.9° 18:05 7.88 46% 138.4°
2040-04-05 Thu 5 — unknown 21:30–21:50 (marginal, 0.33 h) 42.9° 18:00 7.83 35% 128.3°
2040-04-06 Fri 4 — unknown 21:30–21:45 (marginal, 0.25 h) 42.9° 17:55 7.77 24% 117.0°
2040-04-07 Sat 3 — unknown 21:00–21:10 (marginal, 0.17 h) 42.9° 17:50 7.72 16% 105.2°
2040-04-08 Sun 3 — unknown 21:00–21:10 (marginal, 0.17 h) 42.9° 17:50 7.66 8% 93.3°
2040-04-09 Mon 2 — unknown 21:00–21:05 (marginal, 0.08 h) 42.9° 17:45 7.6 3% 81.5°
2040-04-10 Tue 1 — unknown — 42.9° 17:40 7.55 1% 70.0°
2040-04-11 Wed 1 — unknown — 42.9° 17:35 7.49 0% 59.1°
2040-04-12 Thu 1 — unknown — 42.9° 17:35 7.43 2% 48.9°
2040-04-13 Fri 1 — unknown — 42.9° 17:30 7.37 6% 40.2°

Download: CSV · JSON


💡 API
curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2040-03-15&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.