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.

2040-09-04astronomy score per night — click a bar for that night2040-10-03

night of	weather	overall	best window	highest	dark h	Moon	Moon sep.
2040-09-04 Tue	—	unknown	—	50.1° 14:55	7.81	3%	41.9°
2040-09-05 Wed	—	unknown	—	50.1° 14:50	7.87	1%	29.8°
2040-09-06 Thu	—	unknown	—	50.1° 14:45	7.92	0%	17.5°
2040-09-07 Fri	—	unknown	—	50.1° 14:45	7.98	2%	5.1°
2040-09-08 Sat	—	unknown	—	50.1° 14:40	8.03	5%	7.6°
2040-09-09 Sun	—	unknown	—	50.1° 14:35	8.08	11%	20.4°
2040-09-10 Mon	—	unknown	—	50.1° 14:30	8.14	18%	33.5°
2040-09-11 Tue	—	unknown	—	50.1° 14:30	8.19	27%	46.8°
2040-09-12 Wed	—	unknown	—	50.1° 14:25	8.25	37%	60.3°
2040-09-13 Thu	—	unknown	—	50.1° 14:20	8.3	48%	74.0°
2040-09-14 Fri	—	unknown	—	50.1° 14:15	8.35	60%	88.1°
2040-09-15 Sat	—	unknown	—	50.1° 14:10	8.4	70%	102.3°
2040-09-16 Sun	—	unknown	—	50.1° 14:10	8.46	80%	116.8°
2040-09-17 Mon	—	unknown	—	50.1° 14:05	8.51	89%	131.4°
2040-09-18 Tue	—	unknown	—	50.1° 14:00	8.56	95%	146.1°
2040-09-19 Wed	—	unknown	—	50.1° 13:55	8.61	99%	160.8°
2040-09-20 Thu	—	unknown	—	50.1° 13:50	8.66	100%	175.2°
2040-09-21 Fri	—	unknown	—	50.1° 13:50	8.71	98%	170.5°
2040-09-22 Sat	—	unknown	—	50.1° 13:45	8.77	94%	156.7°
2040-09-23 Sun	—	unknown	—	50.1° 13:40	8.82	88%	143.3°
2040-09-24 Mon	—	unknown	—	50.1° 13:35	8.87	80%	130.2°
2040-09-25 Tue	—	unknown	—	50.1° 13:35	8.92	71%	117.6°
2040-09-26 Wed	—	unknown	—	50.1° 13:30	8.97	62%	105.3°
2040-09-27 Thu	—	unknown	—	50.1° 13:25	9.01	53%	93.2°
2040-09-28 Fri	—	unknown	—	50.1° 13:20	9.06	43%	81.3°
2040-09-29 Sat	—	unknown	—	50.1° 13:15	9.11	34%	69.4°
2040-09-30 Sun	—	unknown	—	50.1° 13:15	9.16	25%	57.6°
2040-10-01 Mon	—	unknown	—	50.1° 13:10	9.21	18%	45.7°
2040-10-02 Tue	—	unknown	—	50.1° 13:05	9.26	11%	33.6°
2040-10-03 Wed	—	unknown	—	50.1° 13:00	9.3	6%	21.4°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2040-09-04&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.