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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 HD 189733: 05-21 (97), 05-22 (97), 05-23 (97), 05-24 (97), 05-20 (96) — by astronomy; check the weather when the night is within four days.
2026-05-06astronomy score per night — click a bar for that night2026-06-04
night ofastronomyweatheroverall best windowhighestdark hMoonMoon sep.
2026-05-06 Wed 38 98 37 02:20–04:00 (good, 1.67 h) 71.1° 06:25 6.08 77% 51.6°
2026-05-07 Thu 52 3 1 00:50–01:00 (marginal, 0.17 h) 71.1° 06:20 6.02 69% 47.1°
2026-05-08 Fri 60 25 15 02:00–03:00 (marginal, 1.0 h) 71.1° 06:15 5.96 59% 44.6°
2026-05-09 Sat 67 82 55 01:15–04:00 (good, 2.75 h) 71.1° 06:10 5.91 50% 44.7°
2026-05-10 Sun 74 49 36 02:00–03:00 (good, 1.0 h) 71.1° 06:05 5.85 40% 47.6°
2026-05-11 Mon 80 3 3 00:55–01:00 (marginal, 0.08 h) 71.1° 06:05 5.79 30% 52.9°
2026-05-12 Tue 85 96 81 01:05–04:10 (good, 3.08 h) 71.1° 06:00 5.74 20% 60.2°
2026-05-13 Wed 89 0 0 — 71.1° 05:55 5.68 12% 69.0°
2026-05-14 Thu 90 56 51 01:10–02:00 (good, 0.83 h) 71.1° 05:50 5.63 5% 79.0°
2026-05-15 Fri 90 55 50 01:10–02:00 (good, 0.83 h) 71.1° 05:50 5.58 1% 89.5°
2026-05-16 Sat 92 86 79 01:00–04:05 (good, 3.08 h) 71.1° 05:45 5.52 0% 100.3°
2026-05-17 Sun 94 0 0 — 71.1° 05:40 5.47 2% 110.7°
2026-05-18 Mon 94 5 5 — 71.1° 05:35 5.42 7% 120.3°
2026-05-19 Tue 94 0 0 — 71.1° 05:30 5.37 14% 128.2°
2026-05-20 Wed 96 67 64 01:20–02:00 (good, 0.67 h) 71.1° 05:30 5.32 23% 133.6°
2026-05-21 Thu 97 2 2 — 71.1° 05:25 5.27 33% 135.8°
2026-05-22 Fri 97 6 5 — 71.1° 05:20 5.22 44% 134.5°
2026-05-23 Sat 97 44 43 01:00–02:00 (good, 1.0 h) 71.1° 05:15 5.17 55% 130.4°
2026-05-24 Sun 97 86 84 01:00–03:55 (good, 2.92 h) 71.1° 05:10 5.13 65% 124.2°
2026-05-25 Mon 96 44 42 02:40–03:00 (good, 0.33 h) 71.1° 05:10 5.08 74% 116.8°
2026-05-26 Tue 93 80 74 00:35–03:00 (good, 2.42 h) 71.1° 05:05 5.04 83% 108.7°
2026-05-27 Wed 89 76 68 03:00–03:50 (good, 0.83 h) 71.1° 05:00 4.99 89% 100.2°
2026-05-28 Thu 69 99 69 00:35–03:50 (good, 3.25 h) 71.1° 04:55 4.95 94% 91.5°
2026-05-29 Fri 61 92 56 01:55–03:50 (good, 1.92 h) 71.1° 04:55 4.91 98% 83.0°
2026-05-30 Sat 53 66 35 01:30–03:45 (marginal, 2.25 h) 71.1° 04:50 4.87 100% 74.6°
2026-05-31 Sun 47 97 46 02:00–03:45 (good, 1.75 h) 71.1° 04:45 4.83 100% 66.6°
2026-06-01 Mon 44 29 13 23:30–01:00 (marginal, 1.5 h) 71.1° 04:40 4.79 98% 59.3°
2026-06-02 Tue 42 88 37 23:10–03:45 (marginal, 4.58 h) 71.1° 04:35 4.76 94% 52.9°
2026-06-03 Wed 57 72 41 23:35–23:55 (good, 0.33 h) 71.1° 04:35 4.73 89% 47.8°
2026-06-04 Thu 69 37 26 23:40–00:25 (good, 0.75 h) 71.1° 04:30 4.69 82% 44.8°

Download: CSV · JSON


💡 API
curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2026-05-06&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.