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.

2040-01-13astronomy score per night — click a bar for that night2040-02-11

night of	astronomy	weather	overall	best window	highest	dark h	Moon	Moon sep.
2040-01-13 Fri	89	—	unknown	19:10–01:45 (good, 6.58 h)	42.9° 22:25	11.27	0%	138.6°
2040-01-14 Sat	89	—	unknown	19:10–01:40 (good, 6.5 h)	42.9° 22:25	11.25	1%	127.6°
2040-01-15 Sun	89	—	unknown	19:05–01:40 (good, 6.58 h)	42.9° 22:20	11.23	5%	115.4°
2040-01-16 Mon	89	—	unknown	19:00–01:35 (good, 6.58 h)	42.9° 22:15	11.21	11%	103.1°
2040-01-17 Tue	89	—	unknown	19:00–01:30 (good, 6.5 h)	42.9° 22:10	11.19	19%	90.9°
2040-01-18 Wed	89	—	unknown	19:05–01:25 (good, 6.33 h)	42.9° 22:05	11.17	28%	79.1°
2040-01-19 Thu	86	—	unknown	19:10–01:20 (good, 6.17 h)	42.9° 22:05	11.14	38%	67.9°
2040-01-20 Fri	80	—	unknown	19:30–01:20 (good, 5.83 h)	42.9° 22:00	11.12	48%	57.3°
2040-01-21 Sat	61	—	unknown	21:55–00:45 (good, 2.83 h)	42.9° 21:55	11.09	58%	47.7°
2040-01-22 Sun	43	—	unknown	19:05–01:35 (marginal, 6.5 h)	42.9° 21:50	11.07	68%	39.3°
2040-01-23 Mon	28	—	unknown	19:05–01:20 (marginal, 6.25 h)	42.9° 21:45	11.04	76%	32.9°
2040-01-24 Tue	18	—	unknown	19:05–00:50 (marginal, 5.75 h)	42.9° 21:45	11.01	84%	29.7°
2040-01-25 Wed	13	—	unknown	—	42.9° 21:40	10.98	90%	30.6°
2040-01-26 Thu	14	—	unknown	19:05–19:50 (marginal, 0.75 h)	42.9° 21:35	10.96	95%	35.3°
2040-01-27 Fri	18	—	unknown	19:10–21:55 (marginal, 2.75 h)	42.9° 21:30	10.93	98%	42.6°
2040-01-28 Sat	25	—	unknown	19:10–00:05 (marginal, 4.92 h)	42.9° 21:30	10.9	100%	51.4°
2040-01-29 Sun	36	—	unknown	19:10–00:30 (marginal, 5.33 h)	42.9° 21:25	10.87	100%	61.2°
2040-01-30 Mon	50	—	unknown	19:10–20:10 (good, 1.0 h)	42.9° 21:20	10.83	97%	71.5°
2040-01-31 Tue	82	—	unknown	19:15–22:45 (good, 3.5 h)	42.9° 21:15	10.8	93%	82.2°
2040-02-01 Wed	88	—	unknown	19:15–00:00 (good, 4.75 h)	42.9° 21:10	10.77	88%	93.2°
2040-02-02 Thu	89	—	unknown	19:15–00:10 (good, 4.92 h)	42.9° 21:10	10.74	80%	104.3°
2040-02-03 Fri	89	—	unknown	19:15–00:15 (good, 5.0 h)	42.9° 21:05	10.7	71%	115.4°
2040-02-04 Sat	89	—	unknown	19:15–00:15 (good, 5.0 h)	42.9° 21:00	10.67	61%	126.2°
2040-02-05 Sun	89	—	unknown	19:20–00:15 (good, 4.92 h)	42.9° 20:55	10.64	50%	136.4°
2040-02-06 Mon	89	—	unknown	19:20–00:10 (good, 4.83 h)	42.9° 20:50	10.6	39%	144.9°
2040-02-07 Tue	89	—	unknown	19:20–00:05 (good, 4.75 h)	42.9° 20:50	10.56	28%	149.9°
2040-02-08 Wed	89	—	unknown	19:20–00:05 (good, 4.75 h)	42.9° 20:45	10.53	18%	149.1°
2040-02-09 Thu	89	—	unknown	19:25–00:00 (good, 4.58 h)	42.9° 20:40	10.49	10%	142.6°
2040-02-10 Fri	89	—	unknown	19:25–23:55 (good, 4.5 h)	42.9° 20:35	10.45	4%	132.7°
2040-02-11 Sat	89	—	unknown	19:25–23:50 (good, 4.42 h)	42.9° 20:35	10.42	1%	121.1°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2040-01-13&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.