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: 01-23 (89), 01-24 (89), 01-25 (89), 01-26 (89), 02-11 (89) — by astronomy; check the weather when the night is within four days.

2031-01-23astronomy score per night — click a bar for that night2031-02-21

night of	astronomy	weather	overall	best window	highest	dark h	Moon	Moon sep.
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°
2031-02-11 Tue	89	—	unknown	19:25–23:35 (good, 4.17 h)	42.9° 20:30	10.41	81%	107.4°
2031-02-12 Wed	89	—	unknown	19:25–23:40 (good, 4.25 h)	42.9° 20:25	10.37	72%	119.0°
2031-02-13 Thu	89	—	unknown	19:25–23:45 (good, 4.33 h)	42.9° 20:25	10.33	61%	130.4°
2031-02-14 Fri	89	—	unknown	19:30–23:40 (good, 4.17 h)	42.9° 20:20	10.29	50%	140.8°
2031-02-15 Sat	88	—	unknown	19:30–23:35 (good, 4.08 h)	42.9° 20:15	10.25	39%	149.2°
2031-02-16 Sun	87	—	unknown	19:30–23:30 (good, 4.0 h)	42.9° 20:10	10.21	28%	153.1°
2031-02-17 Mon	86	—	unknown	19:30–23:25 (good, 3.92 h)	42.9° 20:10	10.17	18%	150.3°
2031-02-18 Tue	83	—	unknown	19:35–23:25 (good, 3.83 h)	42.9° 20:05	10.13	10%	142.1°
2031-02-19 Wed	82	—	unknown	19:35–23:20 (good, 3.75 h)	42.9° 20:00	10.09	4%	131.2°
2031-02-20 Thu	80	—	unknown	19:35–23:15 (good, 3.67 h)	42.9° 19:55	10.05	1%	119.1°
2031-02-21 Fri	79	—	unknown	19:35–23:10 (good, 3.58 h)	42.9° 19:50	10.01	0%	106.6°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2031-01-23&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.