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: 09-09 (25), 09-08 (24), 09-07 (23), 09-06 (22), 09-05 (19) — by astronomy; check the weather when the night is within four days.

2030-08-11astronomy score per night — click a bar for that night2030-09-09

night of	astronomy	weather	overall	best window	highest	dark h	Moon	Moon sep.
2030-08-11 Sun	0	—	unknown	—	42.9° 09:35	6.41	97%	137.4°
2030-08-12 Mon	0	—	unknown	—	42.9° 09:30	6.47	100%	126.3°
2030-08-13 Tue	0	—	unknown	—	42.9° 09:25	6.53	100%	114.6°
2030-08-14 Wed	0	—	unknown	—	42.9° 09:25	6.59	97%	102.7°
2030-08-15 Thu	0	—	unknown	—	42.9° 09:20	6.64	92%	90.9°
2030-08-16 Fri	0	—	unknown	—	42.9° 09:15	6.7	86%	79.4°
2030-08-17 Sat	0	—	unknown	—	42.9° 09:10	6.76	78%	68.4°
2030-08-18 Sun	0	—	unknown	—	42.9° 09:05	6.82	70%	57.9°
2030-08-19 Mon	0	—	unknown	—	42.9° 09:05	6.87	61%	48.1°
2030-08-20 Tue	0	—	unknown	—	42.9° 09:00	6.93	51%	39.3°
2030-08-21 Wed	1	—	unknown	—	42.9° 08:55	6.99	42%	32.2°
2030-08-22 Thu	1	—	unknown	—	42.9° 08:50	7.05	33%	28.2°
2030-08-23 Fri	1	—	unknown	—	42.9° 08:50	7.1	24%	28.4°
2030-08-24 Sat	2	—	unknown	—	42.9° 08:45	7.16	16%	33.0°
2030-08-25 Sun	3	—	unknown	05:30–05:40 (marginal, 0.17 h)	42.9° 08:40	7.22	10%	40.7°
2030-08-26 Mon	4	—	unknown	04:50–05:05 (marginal, 0.25 h)	42.9° 08:35	7.27	5%	50.1°
2030-08-27 Tue	5	—	unknown	04:45–05:05 (marginal, 0.33 h)	42.9° 08:30	7.33	1%	60.8°
2030-08-28 Wed	6	—	unknown	05:15–05:45 (marginal, 0.5 h)	42.9° 08:30	7.39	0%	72.1°
2030-08-29 Thu	8	—	unknown	04:40–05:45 (marginal, 1.08 h)	42.9° 08:25	7.44	1%	83.9°
2030-08-30 Fri	9	—	unknown	05:05–05:10 (good, 0.08 h)	42.9° 08:20	7.5	5%	96.0°
2030-08-31 Sat	10	—	unknown	05:00–05:10 (good, 0.17 h)	42.9° 08:15	7.56	11%	108.2°
2030-09-01 Sun	12	—	unknown	05:00–05:10 (good, 0.17 h)	42.9° 08:10	7.61	18%	120.3°
2030-09-02 Mon	14	—	unknown	04:55–05:15 (good, 0.33 h)	42.9° 08:10	7.67	28%	131.8°
2030-09-03 Tue	15	—	unknown	04:50–05:15 (good, 0.42 h)	42.9° 08:05	7.72	39%	142.1°
2030-09-04 Wed	17	—	unknown	04:45–05:15 (good, 0.5 h)	42.9° 08:00	7.78	50%	149.8°
2030-09-05 Thu	19	—	unknown	04:40–05:15 (good, 0.58 h)	42.9° 07:55	7.83	62%	152.4°
2030-09-06 Fri	22	—	unknown	04:40–05:20 (good, 0.67 h)	42.9° 07:55	7.89	72%	148.7°
2030-09-07 Sat	23	—	unknown	04:35–05:20 (good, 0.75 h)	42.9° 07:50	7.94	82%	140.6°
2030-09-08 Sun	24	—	unknown	04:30–05:20 (good, 0.83 h)	42.9° 07:45	8.0	90%	130.2°
2030-09-09 Mon	25	—	unknown	04:35–05:25 (good, 0.83 h)	42.9° 07:40	8.05	95%	118.8°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2030-08-11&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.