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: 04-07 (3), 04-08 (3), 04-09 (2), 04-10 (1), 04-11 (1) — by astronomy; check the weather when the night is within four days.

2037-04-07astronomy score per night — click a bar for that night2037-05-06

night of	astronomy	weather	overall	best window	highest	dark h	Moon	Moon sep.
2037-04-07 Tue	3	—	unknown	21:35–21:45 (marginal, 0.17 h)	42.9° 17:55	7.73	46%	139.8°
2037-04-08 Wed	3	—	unknown	21:00–21:10 (marginal, 0.17 h)	42.9° 17:50	7.67	36%	130.2°
2037-04-09 Thu	2	—	unknown	21:00–21:05 (marginal, 0.08 h)	42.9° 17:45	7.62	27%	120.1°
2037-04-10 Fri	1	—	unknown	—	42.9° 17:40	7.56	19%	109.6°
2037-04-11 Sat	1	—	unknown	—	42.9° 17:40	7.5	12%	99.0°
2037-04-12 Sun	1	—	unknown	—	42.9° 17:35	7.45	7%	88.3°
2037-04-13 Mon	1	—	unknown	—	42.9° 17:30	7.39	3%	77.5°
2037-04-14 Tue	0	—	unknown	—	42.9° 17:25	7.33	1%	66.8°
2037-04-15 Wed	0	—	unknown	—	42.9° 17:20	7.27	0%	56.1°
2037-04-16 Thu	0	—	unknown	—	42.9° 17:20	7.22	2%	45.7°
2037-04-17 Fri	0	—	unknown	—	42.9° 17:15	7.16	5%	36.3°
2037-04-18 Sat	0	—	unknown	—	42.9° 17:10	7.1	11%	28.7°
2037-04-19 Sun	0	—	unknown	—	42.9° 17:05	7.04	18%	25.4°
2037-04-20 Mon	0	—	unknown	—	42.9° 17:00	6.98	27%	28.0°
2037-04-21 Tue	0	—	unknown	—	42.9° 17:00	6.93	37%	35.5°
2037-04-22 Wed	0	—	unknown	—	42.9° 16:55	6.87	48%	45.7°
2037-04-23 Thu	0	—	unknown	—	42.9° 16:50	6.81	59%	57.4°
2037-04-24 Fri	0	—	unknown	—	42.9° 16:45	6.75	70%	69.9°
2037-04-25 Sat	0	—	unknown	—	42.9° 16:40	6.69	80%	82.9°
2037-04-26 Sun	0	—	unknown	—	42.9° 16:40	6.64	89%	96.2°
2037-04-27 Mon	0	—	unknown	—	42.9° 16:35	6.58	95%	109.4°
2037-04-28 Tue	0	—	unknown	—	42.9° 16:30	6.52	99%	122.3°
2037-04-29 Wed	0	—	unknown	—	42.9° 16:25	6.46	100%	134.4°
2037-04-30 Thu	0	—	unknown	—	42.9° 16:25	6.4	98%	144.9°
2037-05-01 Fri	0	—	unknown	—	42.9° 16:20	6.34	94%	152.4°
2037-05-02 Sat	0	—	unknown	—	42.9° 16:15	6.29	88%	154.5°
2037-05-03 Sun	0	—	unknown	—	42.9° 16:10	6.23	80%	150.5°
2037-05-04 Mon	0	—	unknown	—	42.9° 16:05	6.17	72%	142.7°
2037-05-05 Tue	0	—	unknown	—	42.9° 16:05	6.11	62%	133.3°
2037-05-06 Wed	0	—	unknown	—	42.9° 16:00	6.06	53%	123.2°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2037-04-07&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.