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.

2040-05-11astronomy score per night — click a bar for that night2040-06-09

night of	weather	overall	best window	highest	dark h	Moon	Moon sep.
2040-05-11 Fri	—	unknown	—	42.9° 15:40	5.76	1%	35.5°
2040-05-12 Sat	—	unknown	—	42.9° 15:35	5.71	3%	31.0°
2040-05-13 Sun	—	unknown	—	42.9° 15:30	5.65	7%	30.7°
2040-05-14 Mon	—	unknown	—	42.9° 15:25	5.6	13%	34.3°
2040-05-15 Tue	—	unknown	—	42.9° 15:25	5.55	20%	40.8°
2040-05-16 Wed	—	unknown	—	42.9° 15:20	5.49	28%	49.0°
2040-05-17 Thu	—	unknown	—	42.9° 15:15	5.44	37%	58.2°
2040-05-18 Fri	—	unknown	—	42.9° 15:10	5.39	46%	68.1°
2040-05-19 Sat	—	unknown	—	42.9° 15:05	5.34	56%	78.4°
2040-05-20 Sun	—	unknown	—	42.9° 15:05	5.29	66%	89.2°
2040-05-21 Mon	—	unknown	—	42.9° 15:00	5.24	75%	100.2°
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°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2040-05-11&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.