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 Great Orion Nebula: 04-09 (1) — by astronomy; check the weather when the night is within four days.

2041-04-09astronomy score per night — click a bar for that night2041-05-08

night of	astronomy	weather	overall	best window	highest	dark h	Moon	Moon sep.
2041-04-09 Tue	1	—	unknown	—	42.9° 17:45	7.62	64%	54.3°
2041-04-10 Wed	0	—	unknown	—	42.9° 17:40	7.56	73%	63.7°
2041-04-11 Thu	0	—	unknown	—	42.9° 17:40	7.5	81%	73.4°
2041-04-12 Fri	0	—	unknown	—	42.9° 17:35	7.44	88%	83.5°
2041-04-13 Sat	0	—	unknown	—	42.9° 17:30	7.39	94%	93.7°
2041-04-14 Sun	0	—	unknown	—	42.9° 17:25	7.33	98%	104.1°
2041-04-15 Mon	0	—	unknown	—	42.9° 17:20	7.27	100%	114.4°
2041-04-16 Tue	0	—	unknown	—	42.9° 17:20	7.21	100%	124.5°
2041-04-17 Wed	0	—	unknown	—	42.9° 17:15	7.16	98%	133.9°
2041-04-18 Thu	0	—	unknown	—	42.9° 17:10	7.1	94%	141.9°
2041-04-19 Fri	0	—	unknown	—	42.9° 17:05	7.04	88%	147.1°
2041-04-20 Sat	0	—	unknown	—	42.9° 17:00	6.98	79%	147.9°
2041-04-21 Sun	0	—	unknown	—	42.9° 17:00	6.92	70%	143.8°
2041-04-22 Mon	0	—	unknown	—	42.9° 16:55	6.87	59%	135.9°
2041-04-23 Tue	0	—	unknown	—	42.9° 16:50	6.81	48%	125.9°
2041-04-24 Wed	0	—	unknown	—	42.9° 16:45	6.75	36%	114.7°
2041-04-25 Thu	0	—	unknown	—	42.9° 16:45	6.69	26%	102.8°
2041-04-26 Fri	0	—	unknown	—	42.9° 16:40	6.63	16%	90.7°
2041-04-27 Sat	0	—	unknown	—	42.9° 16:35	6.57	8%	78.5°
2041-04-28 Sun	0	—	unknown	—	42.9° 16:30	6.52	3%	66.5°
2041-04-29 Mon	0	—	unknown	—	42.9° 16:25	6.46	0%	55.3°
2041-04-30 Tue	0	—	unknown	—	42.9° 16:25	6.4	0%	45.2°
2041-05-01 Wed	0	—	unknown	—	42.9° 16:20	6.34	2%	37.2°
2041-05-02 Thu	0	—	unknown	—	42.9° 16:15	6.28	7%	32.5°
2041-05-03 Fri	0	—	unknown	—	42.9° 16:10	6.23	13%	32.3°
2041-05-04 Sat	0	—	unknown	—	42.9° 16:05	6.17	21%	36.3°
2041-05-05 Sun	0	—	unknown	—	42.9° 16:05	6.11	29%	43.0°
2041-05-06 Mon	0	—	unknown	—	42.9° 16:00	6.05	38%	51.4°
2041-05-07 Tue	0	—	unknown	—	42.9° 15:55	6.0	48%	60.5°
2041-05-08 Wed	0	—	unknown	—	42.9° 15:50	5.94	57%	70.2°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2041-04-09&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.