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: 10-17 (89), 10-18 (89), 10-19 (89), 10-16 (88), 10-15 (86) — by astronomy; check the weather when the night is within four days.

2039-09-20astronomy score per night — click a bar for that night2039-10-19

night of	astronomy	weather	overall	best window	highest	dark h	Moon	Moon sep.
2039-09-20 Tue	44	—	unknown	03:45–05:35 (good, 1.83 h)	42.9° 07:00	8.62	8%	125.0°
2039-09-21 Wed	45	—	unknown	03:40–05:35 (good, 1.92 h)	42.9° 06:55	8.68	16%	135.8°
2039-09-22 Thu	48	—	unknown	03:35–05:40 (good, 2.08 h)	42.9° 06:50	8.73	25%	144.9°
2039-09-23 Fri	49	—	unknown	03:35–05:40 (good, 2.08 h)	42.9° 06:45	8.78	36%	150.2°
2039-09-24 Sat	51	—	unknown	03:30–05:40 (good, 2.17 h)	42.9° 06:45	8.83	47%	149.9°
2039-09-25 Sun	52	—	unknown	03:25–05:40 (good, 2.25 h)	42.9° 06:40	8.88	58%	144.0°
2039-09-26 Mon	55	—	unknown	03:20–05:45 (good, 2.42 h)	42.9° 06:35	8.93	69%	134.9°
2039-09-27 Tue	56	—	unknown	03:15–05:45 (good, 2.5 h)	42.9° 06:30	8.98	79%	124.2°
2039-09-28 Wed	57	—	unknown	03:25–05:45 (good, 2.33 h)	42.9° 06:25	9.03	87%	112.8°
2039-09-29 Thu	54	—	unknown	03:30–05:45 (good, 2.25 h)	42.9° 06:25	9.08	94%	101.2°
2039-09-30 Fri	39	—	unknown	03:45–05:45 (good, 2.0 h)	42.9° 06:20	9.12	98%	89.5°
2039-10-01 Sat	31	—	unknown	05:05–05:50 (good, 0.75 h)	42.9° 06:15	9.17	100%	78.1°
2039-10-02 Sun	23	—	unknown	02:50–05:50 (marginal, 3.0 h)	42.9° 06:10	9.22	100%	67.0°
2039-10-03 Mon	17	—	unknown	03:00–05:50 (marginal, 2.83 h)	42.9° 06:10	9.27	97%	56.5°
2039-10-04 Tue	13	—	unknown	03:10–05:50 (marginal, 2.67 h)	42.9° 06:05	9.32	93%	46.8°
2039-10-05 Wed	11	—	unknown	03:15–05:55 (marginal, 2.67 h)	42.9° 06:00	9.36	87%	38.5°
2039-10-06 Thu	11	—	unknown	03:05–05:55 (marginal, 2.83 h)	42.9° 05:55	9.41	80%	32.2°
2039-10-07 Fri	15	—	unknown	02:40–05:55 (marginal, 3.25 h)	42.9° 05:50	9.46	72%	29.4°
2039-10-08 Sat	20	—	unknown	02:20–05:55 (marginal, 3.58 h)	42.9° 05:50	9.5	64%	30.7°
2039-10-09 Sun	30	—	unknown	02:05–05:55 (marginal, 3.83 h)	42.9° 05:45	9.55	54%	35.7°
2039-10-10 Mon	42	—	unknown	02:55–06:00 (good, 3.08 h)	42.9° 05:40	9.59	45%	43.3°
2039-10-11 Tue	54	—	unknown	02:40–06:00 (good, 3.33 h)	42.9° 05:35	9.64	35%	52.4°
2039-10-12 Wed	66	—	unknown	02:25–06:00 (good, 3.58 h)	42.9° 05:30	9.68	26%	62.5°
2039-10-13 Thu	75	—	unknown	02:15–06:00 (good, 3.75 h)	42.9° 05:30	9.73	18%	73.3°
2039-10-14 Fri	83	—	unknown	02:10–06:05 (good, 3.92 h)	42.9° 05:25	9.77	10%	84.7°
2039-10-15 Sat	86	—	unknown	02:05–06:05 (good, 4.0 h)	42.9° 05:20	9.81	5%	96.5°
2039-10-16 Sun	88	—	unknown	02:00–06:05 (good, 4.08 h)	42.9° 05:15	9.86	1%	108.6°
2039-10-17 Mon	89	—	unknown	02:00–06:05 (good, 4.08 h)	42.9° 05:15	9.9	0%	120.6°
2039-10-18 Tue	89	—	unknown	01:55–06:05 (good, 4.17 h)	42.9° 05:10	9.94	2%	132.1°
2039-10-19 Wed	89	—	unknown	01:50–06:10 (good, 4.33 h)	42.9° 05:05	9.99	6%	142.2°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2039-09-20&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.