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: 09-28 (58), 09-29 (58), 09-30 (58), 09-27 (56), 09-26 (55) — by astronomy; check the weather when the night is within four days.

2047-09-05astronomy score per night — click a bar for that night2047-10-04

night of	astronomy	weather	overall	best window	highest	dark h	Moon	Moon sep.
2047-09-05 Thu	8	—	unknown	04:20–05:15 (marginal, 0.92 h)	42.9° 08:00	7.83	97%	85.1°
2047-09-06 Fri	8	—	unknown	04:25–05:20 (marginal, 0.92 h)	42.9° 07:55	7.88	93%	74.7°
2047-09-07 Sat	7	—	unknown	04:30–05:20 (marginal, 0.83 h)	42.9° 07:50	7.94	88%	64.5°
2047-09-08 Sun	6	—	unknown	04:30–05:20 (marginal, 0.83 h)	42.9° 07:45	7.99	81%	54.9°
2047-09-09 Mon	7	—	unknown	04:25–05:20 (marginal, 0.92 h)	42.9° 07:40	8.05	73%	46.0°
2047-09-10 Tue	8	—	unknown	04:15–05:25 (marginal, 1.17 h)	42.9° 07:40	8.1	64%	38.3°
2047-09-11 Wed	10	—	unknown	04:00–05:25 (marginal, 1.42 h)	42.9° 07:35	8.16	55%	32.6°
2047-09-12 Thu	14	—	unknown	03:50–05:25 (marginal, 1.58 h)	42.9° 07:30	8.21	46%	30.3°
2047-09-13 Fri	19	—	unknown	04:40–05:30 (good, 0.83 h)	42.9° 07:25	8.26	36%	32.3°
2047-09-14 Sat	25	—	unknown	04:25–05:30 (good, 1.08 h)	42.9° 07:20	8.32	27%	38.1°
2047-09-15 Sun	30	—	unknown	04:10–05:30 (good, 1.33 h)	42.9° 07:20	8.37	18%	46.7°
2047-09-16 Mon	34	—	unknown	04:00–05:30 (good, 1.5 h)	42.9° 07:15	8.42	10%	56.9°
2047-09-17 Tue	38	—	unknown	03:55–05:30 (good, 1.58 h)	42.9° 07:10	8.47	5%	68.3°
2047-09-18 Wed	41	—	unknown	03:50–05:35 (good, 1.75 h)	42.9° 07:05	8.52	1%	80.4°
2047-09-19 Thu	42	—	unknown	03:50–05:35 (good, 1.75 h)	42.9° 07:05	8.58	0%	92.9°
2047-09-20 Fri	43	—	unknown	03:45–05:35 (good, 1.83 h)	42.9° 07:00	8.63	2%	105.6°
2047-09-21 Sat	45	—	unknown	03:40–05:35 (good, 1.92 h)	42.9° 06:55	8.68	7%	118.1°
2047-09-22 Sun	48	—	unknown	03:35–05:40 (good, 2.08 h)	42.9° 06:50	8.73	14%	129.8°
2047-09-23 Mon	50	—	unknown	03:35–05:40 (good, 2.08 h)	42.9° 06:45	8.78	23%	140.0°
2047-09-24 Tue	51	—	unknown	03:30–05:40 (good, 2.17 h)	42.9° 06:45	8.83	34%	147.3°
2047-09-25 Wed	52	—	unknown	03:25–05:40 (good, 2.25 h)	42.9° 06:40	8.88	45%	149.8°
2047-09-26 Thu	55	—	unknown	03:20–05:45 (good, 2.42 h)	42.9° 06:35	8.93	56%	146.7°
2047-09-27 Fri	56	—	unknown	03:15–05:45 (good, 2.5 h)	42.9° 06:30	8.98	66%	139.6°
2047-09-28 Sat	58	—	unknown	03:15–05:45 (good, 2.5 h)	42.9° 06:25	9.03	76%	130.4°
2047-09-29 Sun	58	—	unknown	03:15–05:45 (good, 2.5 h)	42.9° 06:25	9.08	84%	120.2°
2047-09-30 Mon	58	—	unknown	03:20–05:50 (good, 2.5 h)	42.9° 06:20	9.13	91%	109.6°
2047-10-01 Tue	53	—	unknown	03:25–05:50 (good, 2.42 h)	42.9° 06:15	9.18	96%	98.9°
2047-10-02 Wed	37	—	unknown	04:05–05:50 (good, 1.75 h)	42.9° 06:10	9.22	99%	88.2°
2047-10-03 Thu	29	—	unknown	05:35–05:50 (good, 0.25 h)	42.9° 06:10	9.27	100%	77.7°
2047-10-04 Fri	22	—	unknown	02:45–05:50 (marginal, 3.08 h)	42.9° 06:05	9.32	99%	67.5°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2047-09-05&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.