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: 10-31 (89), 11-01 (89), 11-02 (89), 11-03 (89), 11-04 (89) — by astronomy; check the weather when the night is within four days.

2040-10-12astronomy score per night — click a bar for that night2040-11-10

night of	astronomy	weather	overall	best window	highest	dark h	Moon	Moon sep.
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°
2040-10-15 Mon	86	—	unknown	02:15–06:05 (good, 3.83 h)	42.9° 05:15	9.85	78%	109.7°
2040-10-16 Tue	82	—	unknown	02:20–06:05 (good, 3.75 h)	42.9° 05:15	9.89	87%	97.7°
2040-10-17 Wed	74	—	unknown	02:50–06:05 (good, 3.25 h)	42.9° 05:10	9.93	93%	85.5°
2040-10-18 Thu	46	—	unknown	04:35–06:10 (good, 1.58 h)	42.9° 05:05	9.98	98%	73.6°
2040-10-19 Fri	33	—	unknown	01:50–06:10 (marginal, 4.33 h)	42.9° 05:00	10.02	100%	62.1°
2040-10-20 Sat	22	—	unknown	02:10–06:10 (marginal, 4.0 h)	42.9° 05:00	10.06	99%	51.4°
2040-10-21 Sun	15	—	unknown	03:35–06:10 (marginal, 2.58 h)	42.9° 04:55	10.1	97%	42.1°
2040-10-22 Mon	12	—	unknown	05:00–06:10 (marginal, 1.17 h)	42.9° 04:50	10.14	92%	35.0°
2040-10-23 Tue	13	—	unknown	04:25–06:15 (marginal, 1.83 h)	42.9° 04:45	10.18	86%	31.3°
2040-10-24 Wed	18	—	unknown	01:30–06:15 (marginal, 4.75 h)	42.9° 04:40	10.22	78%	31.9°
2040-10-25 Thu	28	—	unknown	01:10–06:15 (marginal, 5.08 h)	42.9° 04:40	10.26	69%	36.4°
2040-10-26 Fri	41	—	unknown	00:50–06:15 (marginal, 5.42 h)	42.9° 04:35	10.3	60%	43.4°
2040-10-27 Sat	57	—	unknown	01:45–04:50 (good, 4.08 h)	42.9° 03:30	10.34	51%	51.8°
2040-10-28 Sun	72	—	unknown	00:25–05:20 (good, 4.92 h)	42.9° 03:25	10.38	42%	61.1°
2040-10-29 Mon	81	—	unknown	00:10–05:20 (good, 5.17 h)	42.9° 03:20	10.41	32%	70.9°
2040-10-30 Tue	86	—	unknown	00:05–05:20 (good, 5.25 h)	42.9° 03:20	10.45	24%	81.2°
2040-10-31 Wed	89	—	unknown	00:00–05:20 (good, 5.33 h)	42.9° 03:15	10.49	16%	91.7°
2040-11-01 Thu	89	—	unknown	23:55–05:25 (good, 5.5 h)	42.9° 03:10	10.52	9%	102.5°
2040-11-02 Fri	89	—	unknown	23:55–05:25 (good, 5.5 h)	42.9° 03:05	10.56	4%	113.4°
2040-11-03 Sat	89	—	unknown	23:50–05:25 (good, 5.58 h)	42.9° 03:05	10.59	1%	124.1°
2040-11-04 Sun	89	—	unknown	23:45–05:25 (good, 5.67 h)	42.9° 03:00	10.63	0%	134.2°
2040-11-05 Mon	89	—	unknown	23:40–05:25 (good, 5.75 h)	42.9° 02:55	10.66	2%	142.8°
2040-11-06 Tue	89	—	unknown	23:35–05:30 (good, 5.92 h)	42.9° 02:50	10.7	6%	148.1°
2040-11-07 Wed	89	—	unknown	23:35–05:30 (good, 5.92 h)	42.9° 02:45	10.73	12%	148.3°
2040-11-08 Thu	89	—	unknown	23:30–05:30 (good, 6.0 h)	42.9° 02:45	10.76	21%	143.2°
2040-11-09 Fri	89	—	unknown	23:25–05:30 (good, 6.08 h)	42.9° 02:40	10.8	31%	134.4°
2040-11-10 Sat	89	—	unknown	23:20–05:35 (good, 6.25 h)	42.9° 02:35	10.83	42%	123.9°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2040-10-12&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.