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.

2031-05-11astronomy score per night — click a bar for that night2031-06-09

night of	weather	overall	best window	highest	dark h	Moon	Moon sep.
2031-05-11 Sun	—	unknown	—	42.9° 15:40	5.81	71%	140.2°
2031-05-12 Mon	—	unknown	—	42.9° 15:40	5.75	60%	129.1°
2031-05-13 Tue	—	unknown	—	42.9° 15:35	5.7	48%	117.3°
2031-05-14 Wed	—	unknown	—	42.9° 15:30	5.64	38%	105.3°
2031-05-15 Thu	—	unknown	—	42.9° 15:25	5.59	27%	93.3°
2031-05-16 Fri	—	unknown	—	42.9° 15:20	5.54	18%	81.5°
2031-05-17 Sat	—	unknown	—	42.9° 15:20	5.48	11%	70.0°
2031-05-18 Sun	—	unknown	—	42.9° 15:15	5.43	6%	58.9°
2031-05-19 Mon	—	unknown	—	42.9° 15:10	5.38	2%	48.5°
2031-05-20 Tue	—	unknown	—	42.9° 15:05	5.33	0%	39.1°
2031-05-21 Wed	—	unknown	—	42.9° 15:00	5.28	0%	31.4°
2031-05-22 Thu	—	unknown	—	42.9° 15:00	5.23	2%	26.9°
2031-05-23 Fri	—	unknown	—	42.9° 14:55	5.18	6%	27.0°
2031-05-24 Sat	—	unknown	—	42.9° 14:50	5.14	12%	31.5°
2031-05-25 Sun	—	unknown	—	42.9° 14:45	5.09	18%	39.0°
2031-05-26 Mon	—	unknown	—	42.9° 14:40	5.05	26%	48.0°
2031-05-27 Tue	—	unknown	—	42.9° 14:40	5.0	35%	57.9°
2031-05-28 Wed	—	unknown	—	42.9° 14:35	4.96	45%	68.4°
2031-05-29 Thu	—	unknown	—	42.9° 14:30	4.92	55%	79.4°
2031-05-30 Fri	—	unknown	—	42.9° 14:25	4.88	65%	90.7°
2031-05-31 Sat	—	unknown	—	42.9° 14:25	4.84	74%	102.4°
2031-06-01 Sun	—	unknown	—	42.9° 14:20	4.8	83%	114.4°
2031-06-02 Mon	—	unknown	—	42.9° 14:15	4.77	91%	126.4°
2031-06-03 Tue	—	unknown	—	42.9° 14:10	4.73	96%	137.9°
2031-06-04 Wed	—	unknown	—	42.9° 14:05	4.7	100%	147.8°
2031-06-05 Thu	—	unknown	—	42.9° 14:05	4.67	100%	153.3°
2031-06-06 Fri	—	unknown	—	42.9° 14:00	4.64	97%	151.6°
2031-06-07 Sat	—	unknown	—	42.9° 13:55	4.61	91%	143.7°
2031-06-08 Sun	—	unknown	—	42.9° 13:50	4.59	83%	132.7°
2031-06-09 Mon	—	unknown	—	42.9° 13:45	4.56	74%	120.7°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2031-05-11&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.