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.

Best nights for 3C 273: 07-21 (1) — by astronomy; check the weather when the night is within four days.

2031-07-21astronomy score per night — click a bar for that night2031-08-19

night of	astronomy	weather	overall	best window	highest	dark h	Moon	Moon sep.
2031-07-21 Mon	1	—	unknown	—	50.2° 17:55	5.26	5%	42.0°
2031-07-22 Tue	0	—	unknown	—	50.2° 17:50	5.31	10%	30.3°
2031-07-23 Wed	0	—	unknown	—	50.2° 17:45	5.36	17%	18.9°
2031-07-24 Thu	0	—	unknown	—	50.2° 17:45	5.41	25%	9.7°
2031-07-25 Fri	0	—	unknown	—	50.2° 17:40	5.46	34%	11.9°
2031-07-26 Sat	0	—	unknown	—	50.2° 17:35	5.51	45%	22.8°
2031-07-27 Sun	0	—	unknown	—	50.2° 17:30	5.57	55%	35.5°
2031-07-28 Mon	0	—	unknown	—	50.2° 17:30	5.62	66%	48.9°
2031-07-29 Tue	0	—	unknown	—	50.2° 17:25	5.67	77%	62.8°
2031-07-30 Wed	0	—	unknown	—	50.2° 17:20	5.73	86%	77.2°
2031-07-31 Thu	0	—	unknown	—	50.2° 17:15	5.78	93%	92.0°
2031-08-01 Fri	0	—	unknown	—	50.2° 17:10	5.84	98%	106.9°
2031-08-02 Sat	0	—	unknown	—	50.2° 17:10	5.89	100%	121.9°
2031-08-03 Sun	0	—	unknown	—	50.2° 17:05	5.95	99%	136.7°
2031-08-04 Mon	0	—	unknown	—	50.2° 17:00	6.0	95%	151.0°
2031-08-05 Tue	0	—	unknown	—	50.2° 16:55	6.06	88%	164.2°
2031-08-06 Wed	0	—	unknown	—	50.2° 16:50	6.12	80%	171.4°
2031-08-07 Thu	0	—	unknown	—	50.2° 16:50	6.17	71%	163.5°
2031-08-08 Fri	0	—	unknown	—	50.2° 16:45	6.23	61%	151.6°
2031-08-09 Sat	0	—	unknown	—	50.2° 16:40	6.29	51%	139.4°
2031-08-10 Sun	0	—	unknown	—	50.2° 16:35	6.34	41%	127.3°
2031-08-11 Mon	0	—	unknown	—	50.2° 16:30	6.4	32%	115.3°
2031-08-12 Tue	0	—	unknown	—	50.2° 16:30	6.46	23%	103.5°
2031-08-13 Wed	0	—	unknown	—	50.2° 16:25	6.52	16%	91.8°
2031-08-14 Thu	0	—	unknown	—	50.2° 16:20	6.57	10%	80.1°
2031-08-15 Fri	0	—	unknown	—	50.2° 16:15	6.63	5%	68.4°
2031-08-16 Sat	0	—	unknown	—	50.2° 16:15	6.69	2%	56.7°
2031-08-17 Sun	0	—	unknown	—	50.2° 16:10	6.75	0%	44.9°
2031-08-18 Mon	0	—	unknown	—	50.2° 16:05	6.8	1%	33.1°
2031-08-19 Tue	0	—	unknown	—	50.2° 16:00	6.86	3%	21.5°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2031-07-21&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.