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.

2040-05-20astronomy score per night — click a bar for that night2040-06-18

night of	weather	overall	best window	highest	dark h	Moon	Moon sep.
2040-05-20 Sun	—	unknown	—	72.5° 13:15	5.29	66%	109.0°
2040-05-21 Mon	—	unknown	—	72.5° 13:10	5.24	75%	121.8°
2040-05-22 Tue	—	unknown	—	72.5° 13:05	5.19	84%	134.9°
2040-05-23 Wed	—	unknown	—	72.5° 13:05	5.15	91%	148.5°
2040-05-24 Thu	—	unknown	—	72.5° 13:00	5.1	97%	162.4°
2040-05-25 Fri	—	unknown	—	72.5° 12:55	5.05	100%	174.9°
2040-05-26 Sat	—	unknown	—	72.5° 12:50	5.01	100%	167.0°
2040-05-27 Sun	—	unknown	—	72.5° 12:50	4.97	97%	152.5°
2040-05-28 Mon	—	unknown	—	72.5° 12:45	4.93	91%	137.7°
2040-05-29 Tue	—	unknown	—	72.5° 12:40	4.89	84%	123.0°
2040-05-30 Wed	—	unknown	—	72.5° 12:35	4.85	74%	108.5°
2040-05-31 Thu	—	unknown	—	72.5° 12:30	4.81	63%	94.3°
2040-06-01 Fri	—	unknown	—	72.5° 12:30	4.77	52%	80.3°
2040-06-02 Sat	—	unknown	—	72.5° 12:25	4.74	41%	66.8°
2040-06-03 Sun	—	unknown	—	72.5° 12:20	4.71	31%	53.5°
2040-06-04 Mon	—	unknown	—	72.5° 12:15	4.67	21%	40.6°
2040-06-05 Tue	—	unknown	—	72.5° 12:10	4.64	14%	28.0°
2040-06-06 Wed	—	unknown	—	72.5° 12:10	4.62	8%	15.7°
2040-06-07 Thu	—	unknown	—	72.5° 12:00	4.59	3%	5.2°
2040-06-08 Fri	—	unknown	—	72.5° 12:00	4.57	1%	10.5°
2040-06-09 Sat	—	unknown	—	72.5° 11:55	4.54	0%	22.0°
2040-06-10 Sun	—	unknown	—	72.5° 11:50	4.52	1%	33.8°
2040-06-11 Mon	—	unknown	—	72.5° 11:45	4.5	4%	45.6°
2040-06-12 Tue	—	unknown	—	72.5° 11:40	4.49	9%	57.3°
2040-06-13 Wed	—	unknown	—	72.5° 11:35	4.47	15%	69.1°
2040-06-14 Thu	—	unknown	—	72.5° 11:35	4.46	22%	80.9°
2040-06-15 Fri	—	unknown	—	72.5° 11:30	4.45	31%	92.9°
2040-06-16 Sat	—	unknown	—	72.5° 11:25	4.44	40%	105.0°
2040-06-17 Sun	—	unknown	—	72.5° 11:20	4.43	50%	117.4°
2040-06-18 Mon	—	unknown	—	72.5° 11:15	4.43	61%	130.1°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2040-05-20&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.