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.

2031-01-12astronomy score per night — click a bar for that night2031-02-10

night of	astronomy	weather	overall	best window	highest	dark h	Moon	Moon sep.
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°
2031-02-01 Sat	24	—	unknown	19:15–00:40 (marginal, 5.42 h)	42.9° 21:10	10.76	74%	30.2°
2031-02-02 Sun	16	—	unknown	19:15–00:15 (marginal, 5.0 h)	42.9° 21:05	10.73	82%	27.1°
2031-02-03 Mon	13	—	unknown	19:15–19:50 (marginal, 0.58 h)	42.9° 21:05	10.7	88%	28.5°
2031-02-04 Tue	13	—	unknown	19:15–20:30 (marginal, 1.25 h)	42.9° 21:00	10.66	94%	34.0°
2031-02-05 Wed	17	—	unknown	19:20–22:15 (marginal, 2.92 h)	42.9° 20:55	10.63	97%	42.1°
2031-02-06 Thu	25	—	unknown	19:20–23:45 (marginal, 4.42 h)	42.9° 20:50	10.59	100%	51.6°
2031-02-07 Fri	35	—	unknown	19:20–00:00 (marginal, 4.67 h)	42.9° 20:45	10.56	100%	62.0°
2031-02-08 Sat	49	—	unknown	19:20–20:55 (good, 1.58 h)	42.9° 20:45	10.52	98%	72.9°
2031-02-09 Sun	78	—	unknown	19:25–22:45 (good, 3.33 h)	42.9° 20:40	10.48	94%	84.2°
2031-02-10 Mon	87	—	unknown	19:25–23:30 (good, 4.08 h)	42.9° 20:35	10.45	88%	95.8°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2031-01-12&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.