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: 01-13 (89), 01-14 (89), 01-15 (89), 01-16 (89), 01-17 (89) — by astronomy; check the weather when the night is within four days.

2031-01-02astronomy score per night — click a bar for that night2031-01-31

night of	astronomy	weather	overall	best window	highest	dark h	Moon	Moon sep.
2031-01-02 Thu	54	—	unknown	19:45–03:00 (marginal, 7.25 h)	42.9° 23:10	11.44	72%	52.3°
2031-01-03 Fri	37	—	unknown	20:00–02:45 (marginal, 6.75 h)	42.9° 23:05	11.43	81%	42.9°
2031-01-04 Sat	23	—	unknown	21:25–02:25 (marginal, 5.0 h)	42.9° 23:00	11.42	88%	34.8°
2031-01-05 Sun	14	—	unknown	01:40–01:45 (marginal, 0.08 h)	42.9° 22:55	11.4	93%	29.1°
2031-01-06 Mon	11	—	unknown	—	42.9° 22:55	11.39	97%	27.1°
2031-01-07 Tue	11	—	unknown	—	42.9° 22:50	11.38	99%	29.8°
2031-01-08 Wed	17	—	unknown	19:40–21:45 (marginal, 2.08 h)	42.9° 22:45	11.36	100%	36.1°
2031-01-09 Thu	28	—	unknown	19:10–00:35 (marginal, 5.42 h)	42.9° 22:40	11.34	99%	44.6°
2031-01-10 Fri	44	—	unknown	18:50–01:45 (marginal, 6.92 h)	42.9° 22:35	11.33	96%	54.2°
2031-01-11 Sat	82	—	unknown	19:20–21:35 (good, 2.25 h)	42.9° 22:35	11.31	91%	64.7°
2031-01-12 Sun	86	—	unknown	19:15–00:05 (good, 4.83 h)	42.9° 22:30	11.29	84%	75.6°
2031-01-13 Mon	89	—	unknown	19:10–01:15 (good, 6.08 h)	42.9° 22:25	11.27	76%	86.8°
2031-01-14 Tue	89	—	unknown	19:05–01:25 (good, 6.33 h)	42.9° 22:20	11.25	67%	98.3°
2031-01-15 Wed	89	—	unknown	19:05–01:30 (good, 6.42 h)	42.9° 22:20	11.23	56%	109.9°
2031-01-16 Thu	89	—	unknown	19:00–01:35 (good, 6.58 h)	42.9° 22:15	11.21	46%	121.6°
2031-01-17 Fri	89	—	unknown	19:00–01:30 (good, 6.5 h)	42.9° 22:10	11.19	35%	132.9°
2031-01-18 Sat	89	—	unknown	19:00–01:25 (good, 6.42 h)	42.9° 22:05	11.16	24%	143.3°
2031-01-19 Sun	89	—	unknown	19:00–01:20 (good, 6.33 h)	42.9° 22:00	11.14	15%	150.9°
2031-01-20 Mon	89	—	unknown	19:00–01:15 (good, 6.25 h)	42.9° 22:00	11.11	7%	152.7°
2031-01-21 Tue	89	—	unknown	19:00–01:15 (good, 6.25 h)	42.9° 21:55	11.09	2%	147.5°
2031-01-22 Wed	89	—	unknown	19:05–01:10 (good, 6.08 h)	42.9° 21:50	11.06	0%	137.8°
2031-01-23 Thu	89	—	unknown	19:05–01:05 (good, 6.0 h)	42.9° 21:45	11.03	1%	126.0°
2031-01-24 Fri	89	—	unknown	19:05–01:00 (good, 5.92 h)	42.9° 21:40	11.01	4%	113.6°
2031-01-25 Sat	89	—	unknown	19:05–00:55 (good, 5.83 h)	42.9° 21:40	10.98	10%	101.1°
2031-01-26 Sun	89	—	unknown	19:05–00:55 (good, 5.83 h)	42.9° 21:35	10.95	18%	88.9°
2031-01-27 Mon	87	—	unknown	19:10–00:50 (good, 5.67 h)	42.9° 21:30	10.92	27%	77.1°
2031-01-28 Tue	82	—	unknown	19:10–00:45 (good, 5.58 h)	42.9° 21:25	10.89	36%	65.8°
2031-01-29 Wed	69	—	unknown	19:10–00:25 (good, 5.25 h)	42.9° 21:20	10.86	46%	55.1°
2031-01-30 Thu	53	—	unknown	22:05–23:50 (good, 1.75 h)	42.9° 21:20	10.83	56%	45.3°
2031-01-31 Fri	37	—	unknown	19:15–01:00 (marginal, 5.75 h)	42.9° 21:15	10.8	65%	36.7°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2031-01-02&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.