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.

2040-05-22astronomy score per night — click a bar for that night2040-06-20

night of	weather	overall	best window	highest	dark h	Moon	Moon sep.
2040-05-22 Tue	—	unknown	—	42.9° 14:55	5.19	84%	111.5°
2040-05-23 Wed	—	unknown	—	42.9° 14:50	5.15	91%	122.8°
2040-05-24 Thu	—	unknown	—	42.9° 14:50	5.1	97%	133.5°
2040-05-25 Fri	—	unknown	—	42.9° 14:45	5.05	100%	142.9°
2040-05-26 Sat	—	unknown	—	42.9° 14:40	5.01	100%	148.8°
2040-05-27 Sun	—	unknown	—	42.9° 14:35	4.97	97%	148.9°
2040-05-28 Mon	—	unknown	—	42.9° 14:30	4.93	91%	143.1°
2040-05-29 Tue	—	unknown	—	42.9° 14:30	4.89	84%	133.7°
2040-05-30 Wed	—	unknown	—	42.9° 14:25	4.85	74%	122.5°
2040-05-31 Thu	—	unknown	—	42.9° 14:20	4.81	63%	110.8°
2040-06-01 Fri	—	unknown	—	42.9° 14:15	4.77	52%	98.9°
2040-06-02 Sat	—	unknown	—	42.9° 14:10	4.74	41%	87.1°
2040-06-03 Sun	—	unknown	—	42.9° 14:10	4.71	31%	75.7°
2040-06-04 Mon	—	unknown	—	42.9° 14:05	4.67	21%	64.7°
2040-06-05 Tue	—	unknown	—	42.9° 14:00	4.64	14%	54.4°
2040-06-06 Wed	—	unknown	—	42.9° 13:55	4.62	8%	45.0°
2040-06-07 Thu	—	unknown	—	42.9° 13:50	4.59	3%	37.2°
2040-06-08 Fri	—	unknown	—	42.9° 13:50	4.57	1%	31.9°
2040-06-09 Sat	—	unknown	—	42.9° 13:45	4.54	0%	30.3°
2040-06-10 Sun	—	unknown	—	42.9° 13:40	4.52	1%	32.9°
2040-06-11 Mon	—	unknown	—	42.9° 13:35	4.5	4%	38.7°
2040-06-12 Tue	—	unknown	—	42.9° 13:35	4.49	9%	46.5°
2040-06-13 Wed	—	unknown	—	42.9° 13:30	4.47	15%	55.5°
2040-06-14 Thu	—	unknown	—	42.9° 13:25	4.46	22%	65.2°
2040-06-15 Fri	—	unknown	—	42.9° 13:20	4.45	31%	75.3°
2040-06-16 Sat	—	unknown	—	42.9° 13:15	4.44	40%	85.7°
2040-06-17 Sun	—	unknown	—	42.9° 13:15	4.43	50%	96.5°
2040-06-18 Mon	—	unknown	—	42.9° 13:10	4.43	61%	107.4°
2040-06-19 Tue	—	unknown	—	42.9° 13:05	4.42	71%	118.4°
2040-06-20 Wed	—	unknown	—	42.9° 13:00	4.42	80%	129.2°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2040-05-22&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.