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: 01-15 (89), 01-16 (89), 01-17 (89), 01-18 (89), 01-19 (89) — by astronomy; check the weather when the night is within four days.

2039-01-03astronomy score per night — click a bar for that night2039-02-01

night of	astronomy	weather	overall	best window	highest	dark h	Moon	Moon sep.
2039-01-03 Mon	73	—	unknown	22:40–02:25 (good, 3.75 h)	42.9° 23:05	11.43	65%	54.7°
2039-01-04 Tue	49	—	unknown	19:40–02:50 (marginal, 7.17 h)	42.9° 23:00	11.42	74%	45.3°
2039-01-05 Wed	32	—	unknown	20:00–02:35 (marginal, 6.58 h)	42.9° 22:55	11.4	82%	37.0°
2039-01-06 Thu	20	—	unknown	22:50–02:05 (marginal, 3.25 h)	42.9° 22:55	11.39	88%	30.7°
2039-01-07 Fri	13	—	unknown	—	42.9° 22:50	11.38	94%	27.8°
2039-01-08 Sat	10	—	unknown	—	42.9° 22:45	11.36	98%	29.6°
2039-01-09 Sun	14	—	unknown	19:55–20:25 (marginal, 0.5 h)	42.9° 22:40	11.34	100%	35.5°
2039-01-10 Mon	22	—	unknown	19:20–23:15 (marginal, 3.92 h)	42.9° 22:35	11.33	100%	44.0°
2039-01-11 Tue	35	—	unknown	18:55–01:30 (marginal, 6.58 h)	42.9° 22:35	11.31	98%	54.0°
2039-01-12 Wed	56	—	unknown	19:15–19:20 (good, 0.08 h)	42.9° 22:30	11.29	94%	65.0°
2039-01-13 Thu	83	—	unknown	19:10–23:25 (good, 4.25 h)	42.9° 22:25	11.27	88%	76.5°
2039-01-14 Fri	88	—	unknown	19:05–01:10 (good, 6.08 h)	42.9° 22:20	11.25	80%	88.3°
2039-01-15 Sat	89	—	unknown	19:05–01:20 (good, 6.25 h)	42.9° 22:20	11.23	70%	100.3°
2039-01-16 Sun	89	—	unknown	19:00–01:25 (good, 6.42 h)	42.9° 22:15	11.21	59%	112.3°
2039-01-17 Mon	89	—	unknown	19:00–01:25 (good, 6.42 h)	42.9° 22:10	11.18	48%	124.2°
2039-01-18 Tue	89	—	unknown	19:00–01:25 (good, 6.42 h)	42.9° 22:05	11.16	37%	135.4°
2039-01-19 Wed	89	—	unknown	19:00–01:20 (good, 6.33 h)	42.9° 22:00	11.14	26%	145.0°
2039-01-20 Thu	89	—	unknown	19:00–01:15 (good, 6.25 h)	42.9° 22:00	11.11	17%	151.2°
2039-01-21 Fri	89	—	unknown	19:00–01:15 (good, 6.25 h)	42.9° 21:55	11.09	9%	151.4°
2039-01-22 Sat	89	—	unknown	19:05–01:10 (good, 6.08 h)	42.9° 21:50	11.06	4%	145.6°
2039-01-23 Sun	89	—	unknown	19:05–01:05 (good, 6.0 h)	42.9° 21:45	11.03	1%	136.1°
2039-01-24 Mon	89	—	unknown	19:05–01:00 (good, 5.92 h)	42.9° 21:40	11.01	0%	125.1°
2039-01-25 Tue	89	—	unknown	19:05–00:55 (good, 5.83 h)	42.9° 21:40	10.98	2%	113.5°
2039-01-26 Wed	89	—	unknown	19:05–00:55 (good, 5.83 h)	42.9° 21:35	10.95	7%	101.8°
2039-01-27 Thu	89	—	unknown	19:10–00:50 (good, 5.67 h)	42.9° 21:30	10.92	13%	90.3°
2039-01-28 Fri	89	—	unknown	19:10–00:45 (good, 5.58 h)	42.9° 21:25	10.89	20%	79.1°
2039-01-29 Sat	86	—	unknown	19:10–00:40 (good, 5.5 h)	42.9° 21:25	10.86	29%	68.3°
2039-01-30 Sun	82	—	unknown	19:10–00:40 (good, 5.5 h)	42.9° 21:20	10.83	38%	58.0°
2039-01-31 Mon	65	—	unknown	19:20–00:15 (good, 4.92 h)	42.9° 21:15	10.79	48%	48.4°
2039-02-01 Tue	48	—	unknown	19:15–01:00 (marginal, 5.75 h)	42.9° 21:10	10.76	57%	39.7°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2039-01-03&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.