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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: 09-12 (30), 09-11 (29), 09-13 (29), 09-10 (27), 09-09 (25) — by astronomy; check the weather when the night is within four days.
2027-08-24astronomy score per night — click a bar for that night2027-09-22
night ofastronomyweatheroverall best windowhighestdark hMoonMoon sep.
2027-08-24 Tue 1 — unknown — 42.9° 08:45 7.15 52% 40.6°
2027-08-25 Wed 2 — unknown — 42.9° 08:40 7.2 41% 34.5°
2027-08-26 Thu 3 — unknown 04:50–05:05 (marginal, 0.25 h) 42.9° 08:35 7.26 30% 32.6°
2027-08-27 Fri 4 — unknown 04:50–05:05 (marginal, 0.25 h) 42.9° 08:35 7.32 20% 36.0°
2027-08-28 Sat 5 — unknown 04:45–05:05 (marginal, 0.33 h) 42.9° 08:30 7.37 11% 43.7°
2027-08-29 Sun 7 — unknown 04:40–05:45 (marginal, 1.08 h) 42.9° 08:25 7.43 5% 54.1°
2027-08-30 Mon 9 — unknown 05:05–05:10 (good, 0.08 h) 42.9° 08:20 7.49 1% 65.9°
2027-08-31 Tue 10 — unknown 05:05–05:10 (good, 0.08 h) 42.9° 08:15 7.54 0% 78.3°
2027-09-01 Wed 11 — unknown 05:00–05:10 (good, 0.17 h) 42.9° 08:15 7.6 2% 90.8°
2027-09-02 Thu 14 — unknown 04:55–05:15 (good, 0.33 h) 42.9° 08:10 7.65 7% 103.0°
2027-09-03 Fri 15 — unknown 04:50–05:15 (good, 0.42 h) 42.9° 08:05 7.71 14% 114.6°
2027-09-04 Sat 17 — unknown 04:45–05:15 (good, 0.5 h) 42.9° 08:00 7.76 22% 125.3°
2027-09-05 Sun 18 — unknown 04:45–05:15 (good, 0.5 h) 42.9° 07:55 7.82 32% 134.7°
2027-09-06 Mon 21 — unknown 04:40–05:20 (good, 0.67 h) 42.9° 07:55 7.87 42% 142.1°
2027-09-07 Tue 22 — unknown 04:35–05:20 (good, 0.75 h) 42.9° 07:50 7.93 52% 146.6°
2027-09-08 Wed 24 — unknown 04:30–05:20 (good, 0.83 h) 42.9° 07:45 7.98 61% 147.3°
2027-09-09 Thu 25 — unknown 04:30–05:20 (good, 0.83 h) 42.9° 07:40 8.04 70% 144.3°
2027-09-10 Fri 27 — unknown 04:25–05:25 (good, 1.0 h) 42.9° 07:40 8.09 79% 138.3°
2027-09-11 Sat 29 — unknown 04:20–05:25 (good, 1.08 h) 42.9° 07:35 8.15 86% 130.6°
2027-09-12 Sun 30 — unknown 04:15–05:25 (good, 1.17 h) 42.9° 07:30 8.2 92% 121.8°
2027-09-13 Mon 29 — unknown 04:25–05:25 (good, 1.0 h) 42.9° 07:25 8.25 96% 112.3°
2027-09-14 Tue 23 — unknown 04:30–05:30 (good, 1.0 h) 42.9° 07:20 8.31 99% 102.3°
2027-09-15 Wed 20 — unknown 04:50–05:30 (good, 0.67 h) 42.9° 07:20 8.36 100% 92.1°
2027-09-16 Thu 16 — unknown 03:40–05:30 (marginal, 1.83 h) 42.9° 07:15 8.41 99% 81.7°
2027-09-17 Fri 13 — unknown 03:45–05:30 (marginal, 1.75 h) 42.9° 07:10 8.46 96% 71.3°
2027-09-18 Sat 11 — unknown 03:50–05:35 (marginal, 1.75 h) 42.9° 07:05 8.52 91% 61.0°
2027-09-19 Sun 10 — unknown 03:55–05:35 (marginal, 1.67 h) 42.9° 07:00 8.57 84% 51.2°
2027-09-20 Mon 10 — unknown 03:50–05:35 (marginal, 1.75 h) 42.9° 07:00 8.62 76% 42.3°
2027-09-21 Tue 12 — unknown 03:35–05:35 (marginal, 2.0 h) 42.9° 06:55 8.67 66% 35.6°
2027-09-22 Wed 17 — unknown 03:15–05:40 (marginal, 2.42 h) 42.9° 06:50 8.72 56% 32.4°

Download: CSV · JSON


💡 API
curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2027-08-24&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.