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: 10-16 (89), 10-15 (87), 10-14 (86), 10-13 (83), 10-12 (82) — by astronomy; check the weather when the night is within four days.

2045-09-17astronomy score per night — click a bar for that night2045-10-16

night of	astronomy	weather	overall	best window	highest	dark h	Moon	Moon sep.
2045-09-17 Sun	40	—	unknown	03:55–05:35 (good, 1.67 h)	42.9° 07:10	8.5	49%	146.9°
2045-09-18 Mon	42	—	unknown	03:50–05:35 (good, 1.75 h)	42.9° 07:05	8.55	58%	145.2°
2045-09-19 Tue	43	—	unknown	03:45–05:35 (good, 1.83 h)	42.9° 07:00	8.6	68%	140.2°
2045-09-20 Wed	45	—	unknown	03:45–05:35 (good, 1.83 h)	42.9° 06:55	8.65	76%	133.1°
2045-09-21 Thu	47	—	unknown	03:40–05:40 (good, 2.0 h)	42.9° 06:55	8.7	84%	124.6°
2045-09-22 Fri	47	—	unknown	03:45–05:40 (good, 1.92 h)	42.9° 06:50	8.75	90%	115.5°
2045-09-23 Sat	45	—	unknown	03:50–05:40 (good, 1.83 h)	42.9° 06:45	8.81	95%	105.9°
2045-09-24 Sun	34	—	unknown	03:55–05:40 (good, 1.75 h)	42.9° 06:40	8.86	98%	95.9°
2045-09-25 Mon	28	—	unknown	04:50–05:40 (good, 0.83 h)	42.9° 06:35	8.91	100%	85.8°
2045-09-26 Tue	22	—	unknown	03:05–05:45 (marginal, 2.67 h)	42.9° 06:35	8.96	100%	75.6°
2045-09-27 Wed	17	—	unknown	03:15–05:45 (marginal, 2.5 h)	42.9° 06:30	9.0	97%	65.5°
2045-09-28 Thu	14	—	unknown	03:20–05:45 (marginal, 2.42 h)	42.9° 06:25	9.05	93%	55.7°
2045-09-29 Fri	12	—	unknown	03:25–05:45 (marginal, 2.33 h)	42.9° 06:20	9.1	87%	46.6°
2045-09-30 Sat	12	—	unknown	03:15–05:50 (marginal, 2.58 h)	42.9° 06:15	9.15	79%	39.0°
2045-10-01 Sun	15	—	unknown	02:55–05:50 (marginal, 2.92 h)	42.9° 06:15	9.2	70%	34.1°
2045-10-02 Mon	21	—	unknown	02:35–05:50 (marginal, 3.25 h)	42.9° 06:10	9.25	59%	33.3°
2045-10-03 Tue	31	—	unknown	02:20–05:50 (marginal, 3.5 h)	42.9° 06:05	9.29	48%	37.2°
2045-10-04 Wed	43	—	unknown	03:10–05:55 (good, 2.75 h)	42.9° 06:00	9.34	37%	44.9°
2045-10-05 Thu	54	—	unknown	02:55–05:55 (good, 3.0 h)	42.9° 06:00	9.39	26%	54.8°
2045-10-06 Fri	65	—	unknown	02:40–05:55 (good, 3.25 h)	42.9° 05:55	9.43	17%	66.1°
2045-10-07 Sat	72	—	unknown	02:35–05:55 (good, 3.33 h)	42.9° 05:50	9.48	9%	78.2°
2045-10-08 Sun	75	—	unknown	02:30–05:55 (good, 3.42 h)	42.9° 05:45	9.53	3%	90.6°
2045-10-09 Mon	78	—	unknown	02:30–06:00 (good, 3.5 h)	42.9° 05:40	9.57	0%	102.9°
2045-10-10 Tue	79	—	unknown	02:25–06:00 (good, 3.58 h)	42.9° 05:40	9.62	0%	114.8°
2045-10-11 Wed	80	—	unknown	02:20–06:00 (good, 3.67 h)	42.9° 05:35	9.66	3%	125.8°
2045-10-12 Thu	82	—	unknown	02:15–06:00 (good, 3.75 h)	42.9° 05:30	9.71	8%	135.4°
2045-10-13 Fri	83	—	unknown	02:10–06:00 (good, 3.83 h)	42.9° 05:25	9.75	15%	142.8°
2045-10-14 Sat	86	—	unknown	02:10–06:05 (good, 3.92 h)	42.9° 05:20	9.79	23%	146.7°
2045-10-15 Sun	87	—	unknown	02:05–06:05 (good, 4.0 h)	42.9° 05:20	9.84	32%	146.4°
2045-10-16 Mon	89	—	unknown	02:00–06:05 (good, 4.08 h)	42.9° 05:15	9.88	42%	142.3°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2045-09-17&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.