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.

2037-04-21astronomy score per night — click a bar for that night2037-05-20

night of	weather	overall	best window	highest	dark h	Moon	Moon sep.
2037-04-21 Tue	—	unknown	—	42.9° 17:00	6.93	37%	35.5°
2037-04-22 Wed	—	unknown	—	42.9° 16:55	6.87	48%	45.7°
2037-04-23 Thu	—	unknown	—	42.9° 16:50	6.81	59%	57.4°
2037-04-24 Fri	—	unknown	—	42.9° 16:45	6.75	70%	69.9°
2037-04-25 Sat	—	unknown	—	42.9° 16:40	6.69	80%	82.9°
2037-04-26 Sun	—	unknown	—	42.9° 16:40	6.64	89%	96.2°
2037-04-27 Mon	—	unknown	—	42.9° 16:35	6.58	95%	109.4°
2037-04-28 Tue	—	unknown	—	42.9° 16:30	6.52	99%	122.3°
2037-04-29 Wed	—	unknown	—	42.9° 16:25	6.46	100%	134.4°
2037-04-30 Thu	—	unknown	—	42.9° 16:25	6.4	98%	144.9°
2037-05-01 Fri	—	unknown	—	42.9° 16:20	6.34	94%	152.4°
2037-05-02 Sat	—	unknown	—	42.9° 16:15	6.29	88%	154.5°
2037-05-03 Sun	—	unknown	—	42.9° 16:10	6.23	80%	150.5°
2037-05-04 Mon	—	unknown	—	42.9° 16:05	6.17	72%	142.7°
2037-05-05 Tue	—	unknown	—	42.9° 16:05	6.11	62%	133.3°
2037-05-06 Wed	—	unknown	—	42.9° 16:00	6.06	53%	123.2°
2037-05-07 Thu	—	unknown	—	42.9° 15:55	6.0	43%	112.8°
2037-05-08 Fri	—	unknown	—	42.9° 15:50	5.94	34%	102.2°
2037-05-09 Sat	—	unknown	—	42.9° 15:45	5.89	25%	91.5°
2037-05-10 Sun	—	unknown	—	42.9° 15:45	5.83	18%	80.8°
2037-05-11 Mon	—	unknown	—	42.9° 15:40	5.78	11%	70.0°
2037-05-12 Tue	—	unknown	—	42.9° 15:35	5.72	6%	59.3°
2037-05-13 Wed	—	unknown	—	42.9° 15:30	5.67	2%	48.8°
2037-05-14 Thu	—	unknown	—	42.9° 15:30	5.61	0%	38.9°
2037-05-15 Fri	—	unknown	—	42.9° 15:25	5.56	1%	30.6°
2037-05-16 Sat	—	unknown	—	42.9° 15:20	5.51	3%	25.8°
2037-05-17 Sun	—	unknown	—	42.9° 15:15	5.46	8%	27.0°
2037-05-18 Mon	—	unknown	—	42.9° 15:10	5.4	15%	33.6°
2037-05-19 Tue	—	unknown	—	42.9° 15:10	5.35	24%	43.4°
2037-05-20 Wed	—	unknown	—	42.9° 15:05	5.3	34%	54.8°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2037-04-21&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.