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: 09-26 (55), 09-27 (54), 09-25 (52), 09-24 (51), 09-28 (51) — by astronomy; check the weather when the night is within four days.

2031-09-01astronomy score per night — click a bar for that night2031-09-30

night of	astronomy	weather	overall	best window	highest	dark h	Moon	Moon sep.
2031-09-01 Mon	6	—	unknown	04:30–05:10 (marginal, 0.67 h)	42.9° 08:15	7.6	99%	97.7°
2031-09-02 Tue	6	—	unknown	04:30–05:15 (marginal, 0.75 h)	42.9° 08:10	7.66	97%	84.8°
2031-09-03 Wed	5	—	unknown	04:35–05:15 (marginal, 0.67 h)	42.9° 08:05	7.71	92%	72.3°
2031-09-04 Thu	5	—	unknown	04:40–05:15 (marginal, 0.58 h)	42.9° 08:00	7.77	84%	60.4°
2031-09-05 Fri	5	—	unknown	04:40–05:15 (marginal, 0.58 h)	42.9° 07:55	7.82	76%	49.3°
2031-09-06 Sat	6	—	unknown	04:30–05:20 (marginal, 0.83 h)	42.9° 07:55	7.88	67%	39.4°
2031-09-07 Sun	7	—	unknown	04:20–05:20 (marginal, 1.0 h)	42.9° 07:50	7.93	57%	31.4°
2031-09-08 Mon	10	—	unknown	04:05–05:20 (marginal, 1.25 h)	42.9° 07:45	7.99	48%	26.6°
2031-09-09 Tue	14	—	unknown	05:15–05:20 (good, 0.08 h)	42.9° 07:40	8.04	38%	26.5°
2031-09-10 Wed	18	—	unknown	04:45–05:25 (good, 0.67 h)	42.9° 07:40	8.09	29%	31.0°
2031-09-11 Thu	23	—	unknown	04:30–05:25 (good, 0.92 h)	42.9° 07:35	8.15	21%	38.4°
2031-09-12 Fri	27	—	unknown	04:20–05:25 (good, 1.08 h)	42.9° 07:30	8.2	14%	47.4°
2031-09-13 Sat	30	—	unknown	04:10–05:25 (good, 1.25 h)	42.9° 07:25	8.26	8%	57.4°
2031-09-14 Sun	34	—	unknown	04:10–05:30 (good, 1.33 h)	42.9° 07:20	8.31	4%	68.0°
2031-09-15 Mon	35	—	unknown	04:05–05:30 (good, 1.42 h)	42.9° 07:20	8.36	1%	79.0°
2031-09-16 Tue	37	—	unknown	04:00–05:30 (good, 1.5 h)	42.9° 07:15	8.41	0%	90.2°
2031-09-17 Wed	38	—	unknown	03:55–05:30 (good, 1.58 h)	42.9° 07:10	8.47	2%	101.7°
2031-09-18 Thu	41	—	unknown	03:50–05:35 (good, 1.75 h)	42.9° 07:05	8.52	5%	113.3°
2031-09-19 Fri	43	—	unknown	03:50–05:35 (good, 1.75 h)	42.9° 07:00	8.57	10%	124.7°
2031-09-20 Sat	44	—	unknown	03:45–05:35 (good, 1.83 h)	42.9° 07:00	8.62	18%	135.7°
2031-09-21 Sun	45	—	unknown	03:40–05:35 (good, 1.92 h)	42.9° 06:55	8.67	27%	145.5°
2031-09-22 Mon	48	—	unknown	03:35–05:40 (good, 2.08 h)	42.9° 06:50	8.72	37%	152.5°
2031-09-23 Tue	49	—	unknown	03:35–05:40 (good, 2.08 h)	42.9° 06:45	8.77	48%	153.9°
2031-09-24 Wed	51	—	unknown	03:30–05:40 (good, 2.17 h)	42.9° 06:45	8.82	60%	148.9°
2031-09-25 Thu	52	—	unknown	03:25–05:40 (good, 2.25 h)	42.9° 06:40	8.87	71%	139.5°
2031-09-26 Fri	55	—	unknown	03:20–05:45 (good, 2.42 h)	42.9° 06:35	8.92	81%	128.1°
2031-09-27 Sat	54	—	unknown	03:25–05:45 (good, 2.33 h)	42.9° 06:30	8.97	89%	115.7°
2031-09-28 Sun	51	—	unknown	03:35–05:45 (good, 2.17 h)	42.9° 06:25	9.02	95%	102.9°
2031-09-29 Mon	35	—	unknown	04:05–05:45 (good, 1.67 h)	42.9° 06:25	9.07	99%	90.1°
2031-09-30 Tue	26	—	unknown	02:50–06:20 (marginal, 3.5 h)	42.9° 06:20	9.12	100%	77.4°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2031-09-01&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.