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: 01-05 (89), 01-06 (89), 01-07 (89), 01-08 (89), 01-09 (89) — by astronomy; check the weather when the night is within four days.

2040-01-01astronomy score per night — click a bar for that night2040-01-30

night of	astronomy	weather	overall	best window	highest	dark h	Moon	Moon sep.
2040-01-01 Sun	37	—	unknown	19:35–02:15 (marginal, 6.67 h)	42.9° 23:15	11.45	95%	53.8°
2040-01-02 Mon	53	—	unknown	19:25–02:35 (marginal, 7.17 h)	42.9° 23:10	11.44	90%	63.7°
2040-01-03 Tue	82	—	unknown	19:50–00:05 (good, 4.25 h)	42.9° 23:05	11.43	83%	74.1°
2040-01-04 Wed	87	—	unknown	19:50–01:45 (good, 5.92 h)	42.9° 23:00	11.42	75%	84.8°
2040-01-05 Thu	89	—	unknown	19:45–02:00 (good, 6.25 h)	42.9° 23:00	11.41	66%	95.8°
2040-01-06 Fri	89	—	unknown	19:40–02:05 (good, 6.42 h)	42.9° 22:55	11.39	56%	106.9°
2040-01-07 Sat	89	—	unknown	19:35–02:05 (good, 6.5 h)	42.9° 22:50	11.38	45%	118.2°
2040-01-08 Sun	89	—	unknown	19:30–02:05 (good, 6.58 h)	42.9° 22:45	11.36	34%	129.2°
2040-01-09 Mon	89	—	unknown	19:30–02:00 (good, 6.5 h)	42.9° 22:40	11.35	24%	139.3°
2040-01-10 Tue	89	—	unknown	19:25–01:55 (good, 6.5 h)	42.9° 22:40	11.33	15%	147.3°
2040-01-11 Wed	89	—	unknown	19:20–01:55 (good, 6.58 h)	42.9° 22:35	11.31	7%	150.5°
2040-01-12 Thu	89	—	unknown	19:15–01:50 (good, 6.58 h)	42.9° 22:30	11.29	2%	147.1°
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°

Download: CSV · JSON

💡 API

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