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: 12-15 (89), 12-16 (89), 12-17 (89), 12-18 (89), 12-19 (89) — by astronomy; check the weather when the night is within four days.

2041-12-09astronomy score per night — click a bar for that night2042-01-07

night of	astronomy	weather	overall	best window	highest	dark h	Moon	Moon sep.
2041-12-09 Mon	19	—	unknown	21:35–00:45 (marginal, 3.17 h)	42.9° 00:40	11.45	94%	39.6°
2041-12-10 Tue	32	—	unknown	21:05–03:35 (marginal, 6.5 h)	42.9° 00:40	11.46	89%	47.6°
2041-12-11 Wed	48	—	unknown	20:50–03:55 (marginal, 7.08 h)	42.9° 00:35	11.47	82%	56.6°
2041-12-12 Thu	67	—	unknown	21:40–01:00 (good, 3.33 h)	42.9° 00:30	11.47	74%	66.3°
2041-12-13 Fri	84	—	unknown	21:10–02:55 (good, 5.75 h)	42.9° 00:25	11.48	65%	76.1°
2041-12-14 Sat	88	—	unknown	21:10–03:20 (good, 6.17 h)	42.9° 00:25	11.49	56%	86.1°
2041-12-15 Sun	89	—	unknown	21:05–03:25 (good, 6.33 h)	42.9° 00:20	11.49	47%	96.1°
2041-12-16 Mon	89	—	unknown	21:00–03:25 (good, 6.42 h)	42.9° 00:15	11.5	37%	106.0°
2041-12-17 Tue	89	—	unknown	20:55–03:25 (good, 6.5 h)	42.9° 00:10	11.5	28%	115.9°
2041-12-18 Wed	89	—	unknown	20:55–03:25 (good, 6.5 h)	42.9° 00:05	11.5	20%	125.4°
2041-12-19 Thu	89	—	unknown	20:50–03:20 (good, 6.5 h)	42.9° 00:05	11.51	13%	134.3°
2041-12-20 Fri	89	—	unknown	20:45–03:20 (good, 6.58 h)	42.9° 00:00	11.51	7%	141.9°
2041-12-21 Sat	89	—	unknown	20:40–03:15 (good, 6.58 h)	42.9° 23:55	11.51	2%	146.7°
2041-12-22 Sun	89	—	unknown	20:35–03:10 (good, 6.58 h)	42.9° 23:50	11.51	0%	147.2°
2041-12-23 Mon	89	—	unknown	20:35–03:05 (good, 6.5 h)	42.9° 23:45	11.51	1%	142.9°
2041-12-24 Tue	89	—	unknown	20:30–03:00 (good, 6.5 h)	42.9° 23:45	11.5	3%	134.9°
2041-12-25 Wed	89	—	unknown	20:25–03:00 (good, 6.58 h)	42.9° 23:40	11.5	9%	124.8°
2041-12-26 Thu	89	—	unknown	20:20–02:55 (good, 6.58 h)	42.9° 23:35	11.49	16%	113.5°
2041-12-27 Fri	89	—	unknown	20:20–02:50 (good, 6.5 h)	42.9° 23:30	11.49	26%	101.7°
2041-12-28 Sat	89	—	unknown	20:25–02:45 (good, 6.33 h)	42.9° 23:25	11.48	36%	89.7°
2041-12-29 Sun	88	—	unknown	20:30–02:45 (good, 6.25 h)	42.9° 23:25	11.48	48%	77.7°
2041-12-30 Mon	84	—	unknown	21:00–02:40 (good, 5.67 h)	42.9° 23:20	11.47	59%	66.2°
2041-12-31 Tue	62	—	unknown	23:50–02:05 (good, 2.25 h)	42.9° 23:15	11.46	70%	55.2°
2042-01-01 Wed	41	—	unknown	20:00–02:55 (marginal, 6.92 h)	42.9° 23:10	11.45	79%	45.4°
2042-01-02 Thu	25	—	unknown	20:30–02:35 (marginal, 6.08 h)	42.9° 23:10	11.44	87%	37.6°
2042-01-03 Fri	15	—	unknown	01:30–01:55 (marginal, 0.42 h)	42.9° 23:05	11.43	94%	33.0°
2042-01-04 Sat	11	—	unknown	—	42.9° 23:00	11.41	98%	33.0°
2042-01-05 Sun	14	—	unknown	20:15–20:20 (marginal, 0.08 h)	42.9° 22:55	11.4	100%	37.3°
2042-01-06 Mon	21	—	unknown	19:35–23:25 (marginal, 3.83 h)	42.9° 22:50	11.39	100%	44.5°
2042-01-07 Tue	34	—	unknown	19:15–01:40 (marginal, 6.42 h)	42.9° 22:50	11.37	97%	53.3°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2041-12-09&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.