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: 10-14 (86), 10-13 (84), 10-12 (82), 10-11 (81), 10-10 (80) — by astronomy; check the weather when the night is within four days.

2040-09-15astronomy score per night — click a bar for that night2040-10-14

night of	astronomy	weather	overall	best window	highest	dark h	Moon	Moon sep.
2040-09-15 Sat	36	—	unknown	04:00–05:30 (good, 1.5 h)	42.9° 07:15	8.4	70%	139.5°
2040-09-16 Sun	38	—	unknown	03:55–05:30 (good, 1.58 h)	42.9° 07:10	8.46	80%	129.5°
2040-09-17 Mon	40	—	unknown	03:55–05:35 (good, 1.67 h)	42.9° 07:10	8.51	89%	118.0°
2040-09-18 Tue	38	—	unknown	04:05–05:35 (good, 1.5 h)	42.9° 07:05	8.56	95%	105.8°
2040-09-19 Wed	27	—	unknown	04:15–05:35 (good, 1.33 h)	42.9° 07:00	8.61	99%	93.3°
2040-09-20 Thu	22	—	unknown	05:25–05:35 (good, 0.17 h)	42.9° 06:55	8.66	100%	80.9°
2040-09-21 Fri	17	—	unknown	03:30–05:40 (marginal, 2.17 h)	42.9° 06:50	8.71	98%	68.9°
2040-09-22 Sat	12	—	unknown	03:40–05:40 (marginal, 2.0 h)	42.9° 06:50	8.77	94%	57.6°
2040-09-23 Sun	10	—	unknown	03:45–05:40 (marginal, 1.92 h)	42.9° 06:45	8.82	88%	47.4°
2040-09-24 Mon	10	—	unknown	03:40–05:40 (marginal, 2.0 h)	42.9° 06:40	8.87	80%	38.9°
2040-09-25 Tue	12	—	unknown	03:25–05:45 (marginal, 2.33 h)	42.9° 06:35	8.92	71%	33.0°
2040-09-26 Wed	16	—	unknown	03:05–05:45 (marginal, 2.67 h)	42.9° 06:30	8.97	62%	30.9°
2040-09-27 Thu	22	—	unknown	02:50–05:45 (marginal, 2.92 h)	42.9° 06:30	9.01	53%	33.0°
2040-09-28 Fri	30	—	unknown	03:45–05:45 (good, 2.0 h)	42.9° 06:25	9.06	43%	38.5°
2040-09-29 Sat	40	—	unknown	03:25–05:45 (good, 2.33 h)	42.9° 06:20	9.11	34%	46.0°
2040-09-30 Sun	49	—	unknown	03:10–05:50 (good, 2.67 h)	42.9° 06:15	9.16	25%	54.8°
2040-10-01 Mon	57	—	unknown	03:00–05:50 (good, 2.83 h)	42.9° 06:10	9.21	18%	64.4°
2040-10-02 Tue	63	—	unknown	02:55–05:50 (good, 2.92 h)	42.9° 06:10	9.26	11%	74.4°
2040-10-03 Wed	67	—	unknown	02:50–05:50 (good, 3.0 h)	42.9° 06:05	9.3	6%	84.9°
2040-10-04 Thu	70	—	unknown	02:45–05:55 (good, 3.17 h)	42.9° 06:00	9.35	2%	95.6°
2040-10-05 Fri	71	—	unknown	02:45–05:55 (good, 3.17 h)	42.9° 05:55	9.4	0%	106.4°
2040-10-06 Sat	72	—	unknown	02:40–05:55 (good, 3.25 h)	42.9° 05:55	9.44	1%	117.2°
2040-10-07 Sun	74	—	unknown	02:35–05:55 (good, 3.33 h)	42.9° 05:50	9.49	3%	127.6°
2040-10-08 Mon	76	—	unknown	02:30–05:55 (good, 3.42 h)	42.9° 05:45	9.54	8%	137.2°
2040-10-09 Tue	78	—	unknown	02:25–06:00 (good, 3.58 h)	42.9° 05:40	9.58	15%	144.8°
2040-10-10 Wed	80	—	unknown	02:25–06:00 (good, 3.58 h)	42.9° 05:35	9.63	24%	148.8°
2040-10-11 Thu	81	—	unknown	02:20–06:00 (good, 3.67 h)	42.9° 05:35	9.67	34%	147.5°
2040-10-12 Fri	82	—	unknown	02:15–06:00 (good, 3.75 h)	42.9° 05:30	9.72	45%	141.4°
2040-10-13 Sat	84	—	unknown	02:10–06:05 (good, 3.92 h)	42.9° 05:25	9.76	56%	132.2°
2040-10-14 Sun	86	—	unknown	02:05–06:05 (good, 4.0 h)	42.9° 05:20	9.8	68%	121.4°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2040-09-15&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.