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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: 09-19 (33), 09-18 (26), 09-07 (23), 09-06 (22), 09-08 (22) — by astronomy; check the weather when the night is within four days.
2041-08-21astronomy score per night — click a bar for that night2041-09-19
night ofastronomyweatheroverall best windowhighestdark hMoonMoon sep.
2041-08-21 Wed 1 — unknown — 42.9° 08:55 7.01 20% 35.5°
2041-08-22 Thu 1 — unknown — 42.9° 08:50 7.07 12% 41.7°
2041-08-23 Fri 1 — unknown — 42.9° 08:45 7.12 7% 49.7°
2041-08-24 Sat 2 — unknown 05:30–05:40 (marginal, 0.17 h) 42.9° 08:45 7.18 3% 58.7°
2041-08-25 Sun 4 — unknown 05:25–05:40 (marginal, 0.25 h) 42.9° 08:40 7.24 1% 68.3°
2041-08-26 Mon 4 — unknown 04:50–05:05 (marginal, 0.25 h) 42.9° 08:35 7.29 0% 78.1°
2041-08-27 Tue 5 — unknown 04:45–05:05 (marginal, 0.33 h) 42.9° 08:30 7.35 2% 88.0°
2041-08-28 Wed 7 — unknown 04:40–05:05 (marginal, 0.42 h) 42.9° 08:25 7.41 5% 98.1°
2041-08-29 Thu 8 — unknown 04:40–05:45 (marginal, 1.08 h) 42.9° 08:25 7.46 9% 108.0°
2041-08-30 Fri 9 — unknown 05:05–05:10 (good, 0.08 h) 42.9° 08:20 7.52 16% 117.8°
2041-08-31 Sat 10 — unknown 05:00–05:10 (good, 0.17 h) 42.9° 08:15 7.58 23% 127.2°
2041-09-01 Sun 13 — unknown 04:55–05:15 (good, 0.33 h) 42.9° 08:10 7.63 32% 135.8°
2041-09-02 Mon 15 — unknown 04:55–05:15 (good, 0.33 h) 42.9° 08:10 7.69 42% 142.9°
2041-09-03 Tue 16 — unknown 04:50–05:15 (good, 0.42 h) 42.9° 08:05 7.74 52% 147.2°
2041-09-04 Wed 17 — unknown 04:45–05:15 (good, 0.5 h) 42.9° 08:00 7.8 63% 147.1°
2041-09-05 Thu 21 — unknown 04:40–05:20 (good, 0.67 h) 42.9° 07:55 7.85 73% 142.2°
2041-09-06 Fri 22 — unknown 04:40–05:20 (good, 0.67 h) 42.9° 07:50 7.91 83% 133.8°
2041-09-07 Sat 23 — unknown 04:35–05:20 (good, 0.75 h) 42.9° 07:50 7.96 91% 123.1°
2041-09-08 Sun 22 — unknown 04:45–05:20 (good, 0.58 h) 42.9° 07:45 8.02 96% 111.1°
2041-09-09 Mon 17 — unknown 04:50–05:25 (good, 0.58 h) 42.9° 07:40 8.07 100% 98.4°
2041-09-10 Tue 14 — unknown 03:55–05:25 (marginal, 1.5 h) 42.9° 07:35 8.13 100% 85.5°
2041-09-11 Wed 11 — unknown 04:05–05:25 (marginal, 1.33 h) 42.9° 07:30 8.18 96% 72.9°
2041-09-12 Thu 9 — unknown 04:10–05:25 (marginal, 1.25 h) 42.9° 07:30 8.23 91% 60.8°
2041-09-13 Fri 8 — unknown 04:15–05:30 (marginal, 1.25 h) 42.9° 07:25 8.29 83% 49.9°
2041-09-14 Sat 8 — unknown 04:05–05:30 (marginal, 1.42 h) 42.9° 07:20 8.34 74% 40.8°
2041-09-15 Sun 10 — unknown 03:55–05:30 (marginal, 1.58 h) 42.9° 07:15 8.39 63% 34.5°
2041-09-16 Mon 14 — unknown 03:35–05:30 (marginal, 1.92 h) 42.9° 07:10 8.44 53% 32.3°
2041-09-17 Tue 20 — unknown 03:25–05:35 (marginal, 2.17 h) 42.9° 07:10 8.5 43% 34.5°
2041-09-18 Wed 26 — unknown 04:15–05:35 (good, 1.33 h) 42.9° 07:05 8.55 33% 40.1°
2041-09-19 Thu 33 — unknown 04:00–05:35 (good, 1.58 h) 42.9° 07:00 8.6 25% 47.7°

Download: CSV · JSON


💡 API
curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2041-08-21&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.