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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: 04-24 (67), 04-22 (66), 04-23 (66), 04-25 (66), 04-27 (66) — by astronomy; check the weather when the night is within four days.
2026-04-05astronomy score per night — click a bar for that night2026-05-04
night ofastronomyweatheroverall best windowhighestdark hMoonMoon sep.
2026-04-05 Sun 27 91 25 04:45–05:20 (good, 0.58 h) 71.1° 08:25 7.86 86% 78.4°
2026-04-06 Mon 27 88 24 04:00–05:00 (good, 1.0 h) 71.1° 08:20 7.8 79% 70.3°
2026-04-07 Tue 29 73 21 05:00–05:20 (good, 0.33 h) 71.1° 08:15 7.75 71% 62.7°
2026-04-08 Wed 30 1 0 — 71.1° 08:15 7.69 62% 55.9°
2026-04-09 Thu 35 5 2 02:50–03:00 (marginal, 0.17 h) 71.1° 08:10 7.64 53% 50.2°
2026-04-10 Fri 44 0 0 — 71.1° 08:05 7.58 43% 46.3°
2026-04-11 Sat 49 2 1 — 71.1° 08:00 7.52 33% 44.6°
2026-04-12 Sun 54 0 0 — 71.1° 07:55 7.47 24% 45.6°
2026-04-13 Mon 56 0 0 — 71.1° 07:55 7.41 16% 49.5°
2026-04-14 Tue 58 14 8 02:50–03:00 (good, 0.17 h) 71.1° 07:50 7.35 9% 55.7°
2026-04-15 Wed 59 0 0 — 71.1° 07:45 7.29 3% 63.9°
2026-04-16 Thu 59 34 20 04:00–05:35 (marginal, 1.58 h) 71.1° 07:40 7.24 0% 73.3°
2026-04-17 Fri 61 96 58 02:40–05:00 (good, 2.33 h) 71.1° 07:40 7.18 0% 83.6°
2026-04-18 Sat 62 96 60 02:40–04:55 (good, 2.25 h) 71.1° 07:35 7.12 3% 94.2°
2026-04-19 Sun 63 89 56 02:30–04:55 (good, 2.42 h) 71.1° 07:30 7.06 9% 104.6°
2026-04-20 Mon 63 92 58 02:25–04:50 (good, 2.42 h) 71.1° 07:25 7.0 16% 114.5°
2026-04-21 Tue 65 0 0 — 71.1° 07:20 6.95 26% 123.2°
2026-04-22 Wed 66 0 0 — 71.1° 07:20 6.89 37% 130.0°
2026-04-23 Thu 66 57 38 02:20–04:00 (good, 1.67 h) 71.1° 07:15 6.83 48% 134.3°
2026-04-24 Fri 67 90 60 03:25–04:45 (good, 1.33 h) 71.1° 07:10 6.77 59% 135.5°
2026-04-25 Sat 66 98 64 02:20–04:45 (good, 2.42 h) 71.1° 07:05 6.71 69% 133.5°
2026-04-26 Sun 65 100 65 02:10–04:40 (good, 2.5 h) 71.1° 07:00 6.65 78% 128.9°
2026-04-27 Mon 66 61 41 02:30–03:00 (good, 0.5 h) 71.1° 07:00 6.6 86% 122.4°
2026-04-28 Tue 57 62 35 04:00–04:35 (good, 0.58 h) 71.1° 06:55 6.54 92% 114.8°
2026-04-29 Wed 53 17 9 01:50–02:00 (marginal, 0.17 h) 71.1° 06:50 6.48 97% 106.6°
2026-04-30 Thu 48 0 0 — 71.1° 06:45 6.42 99% 98.0°
2026-05-01 Fri 42 78 33 02:50–04:00 (good, 1.17 h) 71.1° 06:45 6.36 100% 89.4°
2026-05-02 Sat 39 0 0 — 71.1° 06:40 6.31 98% 80.8°
2026-05-03 Sun 37 96 36 03:25–04:30 (good, 1.08 h) 71.1° 06:35 6.25 95% 72.5°
2026-05-04 Mon 35 41 14 03:00–04:25 (marginal, 1.42 h) 71.1° 06:30 6.19 91% 64.7°

Download: CSV · JSON


💡 API
curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2026-04-05&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.