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: 09-25 (52), 09-26 (52), 09-24 (51), 09-23 (50), 09-22 (48) — by astronomy; check the weather when the night is within four days.

2042-09-03astronomy score per night — click a bar for that night2042-10-02

night of	astronomy	weather	overall	best window	highest	dark h	Moon	Moon sep.
2042-09-03 Wed	4	—	unknown	04:45–05:15 (marginal, 0.5 h)	42.9° 08:05	7.73	80%	55.0°
2042-09-04 Thu	5	—	unknown	04:40–05:15 (marginal, 0.58 h)	42.9° 08:00	7.78	70%	45.0°
2042-09-05 Fri	7	—	unknown	04:30–05:20 (marginal, 0.83 h)	42.9° 07:55	7.84	59%	37.4°
2042-09-06 Sat	9	—	unknown	04:15–05:20 (marginal, 1.08 h)	42.9° 07:55	7.89	48%	33.6°
2042-09-07 Sun	13	—	unknown	05:05–05:20 (good, 0.25 h)	42.9° 07:50	7.95	37%	34.5°
2042-09-08 Mon	17	—	unknown	04:50–05:20 (good, 0.5 h)	42.9° 07:45	8.0	27%	39.4°
2042-09-09 Tue	22	—	unknown	04:35–05:25 (good, 0.83 h)	42.9° 07:40	8.06	18%	46.9°
2042-09-10 Wed	26	—	unknown	04:25–05:25 (good, 1.0 h)	42.9° 07:35	8.11	11%	55.9°
2042-09-11 Thu	28	—	unknown	04:20–05:25 (good, 1.08 h)	42.9° 07:35	8.17	6%	65.5°
2042-09-12 Fri	30	—	unknown	04:15–05:25 (good, 1.17 h)	42.9° 07:30	8.22	2%	75.5°
2042-09-13 Sat	33	—	unknown	04:10–05:30 (good, 1.33 h)	42.9° 07:25	8.27	0%	85.6°
2042-09-14 Sun	35	—	unknown	04:05–05:30 (good, 1.42 h)	42.9° 07:20	8.33	0%	95.6°
2042-09-15 Mon	36	—	unknown	04:05–05:30 (good, 1.42 h)	42.9° 07:15	8.38	2%	105.4°
2042-09-16 Tue	37	—	unknown	04:00–05:30 (good, 1.5 h)	42.9° 07:15	8.43	6%	115.0°
2042-09-17 Wed	39	—	unknown	03:55–05:35 (good, 1.67 h)	42.9° 07:10	8.48	11%	124.1°
2042-09-18 Thu	41	—	unknown	03:50–05:35 (good, 1.75 h)	42.9° 07:05	8.54	18%	132.5°
2042-09-19 Fri	43	—	unknown	03:50–05:35 (good, 1.75 h)	42.9° 07:00	8.59	25%	139.7°
2042-09-20 Sat	44	—	unknown	03:45–05:35 (good, 1.83 h)	42.9° 07:00	8.64	34%	144.7°
2042-09-21 Sun	45	—	unknown	03:40–05:35 (good, 1.92 h)	42.9° 06:55	8.69	44%	146.6°
2042-09-22 Mon	48	—	unknown	03:35–05:40 (good, 2.08 h)	42.9° 06:50	8.74	54%	144.5°
2042-09-23 Tue	50	—	unknown	03:30–05:40 (good, 2.17 h)	42.9° 06:45	8.79	64%	138.7°
2042-09-24 Wed	51	—	unknown	03:30–05:40 (good, 2.17 h)	42.9° 06:40	8.84	74%	130.4°
2042-09-25 Thu	52	—	unknown	03:25–05:40 (good, 2.25 h)	42.9° 06:40	8.89	83%	120.2°
2042-09-26 Fri	52	—	unknown	03:35–05:45 (good, 2.17 h)	42.9° 06:35	8.94	91%	108.9°
2042-09-27 Sat	48	—	unknown	03:40–05:45 (good, 2.08 h)	42.9° 06:30	8.99	96%	96.8°
2042-09-28 Sun	31	—	unknown	04:40–05:45 (good, 1.08 h)	42.9° 06:25	9.04	100%	84.2°
2042-09-29 Mon	23	—	unknown	03:00–05:45 (marginal, 2.75 h)	42.9° 06:20	9.09	100%	71.7°
2042-09-30 Tue	16	—	unknown	03:10–05:50 (marginal, 2.67 h)	42.9° 06:20	9.14	97%	59.6°
2042-10-01 Wed	12	—	unknown	03:20–05:50 (marginal, 2.5 h)	42.9° 06:15	9.19	91%	48.6°
2042-10-02 Thu	11	—	unknown	03:15–05:50 (marginal, 2.58 h)	42.9° 06:10	9.23	83%	39.7°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2042-09-03&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.