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: 04-11 (1), 04-12 (1), 04-13 (1), 04-14 (1) — by astronomy; check the weather when the night is within four days.

2039-04-11astronomy score per night — click a bar for that night2039-05-10

night of	astronomy	weather	overall	best window	highest	dark h	Moon	Moon sep.
2039-04-11 Mon	1	—	unknown	—	42.9° 17:40	7.53	89%	146.1°
2039-04-12 Tue	1	—	unknown	—	42.9° 17:35	7.47	80%	151.2°
2039-04-13 Wed	1	—	unknown	—	42.9° 17:30	7.42	70%	150.0°
2039-04-14 Thu	1	—	unknown	—	42.9° 17:30	7.36	59%	143.4°
2039-04-15 Fri	0	—	unknown	—	42.9° 17:25	7.3	48%	133.9°
2039-04-16 Sat	0	—	unknown	—	42.9° 17:20	7.24	37%	123.3°
2039-04-17 Sun	0	—	unknown	—	42.9° 17:15	7.19	27%	112.2°
2039-04-18 Mon	0	—	unknown	—	42.9° 17:10	7.13	19%	101.0°
2039-04-19 Tue	0	—	unknown	—	42.9° 17:10	7.07	12%	89.9°
2039-04-20 Wed	0	—	unknown	—	42.9° 17:05	7.01	6%	78.9°
2039-04-21 Thu	0	—	unknown	—	42.9° 17:00	6.95	2%	68.2°
2039-04-22 Fri	0	—	unknown	—	42.9° 16:55	6.9	0%	58.0°
2039-04-23 Sat	0	—	unknown	—	42.9° 16:50	6.84	0%	48.3°
2039-04-24 Sun	0	—	unknown	—	42.9° 16:50	6.78	2%	39.7°
2039-04-25 Mon	0	—	unknown	—	42.9° 16:45	6.72	6%	32.9°
2039-04-26 Tue	0	—	unknown	—	42.9° 16:40	6.66	11%	29.0°
2039-04-27 Wed	0	—	unknown	—	42.9° 16:35	6.6	17%	29.3°
2039-04-28 Thu	0	—	unknown	—	42.9° 16:35	6.55	25%	33.6°
2039-04-29 Fri	0	—	unknown	—	42.9° 16:30	6.49	34%	40.9°
2039-04-30 Sat	0	—	unknown	—	42.9° 16:25	6.43	43%	49.9°
2039-05-01 Sun	0	—	unknown	—	42.9° 16:20	6.37	53%	60.0°
2039-05-02 Mon	0	—	unknown	—	42.9° 16:15	6.31	64%	71.0°
2039-05-03 Tue	0	—	unknown	—	42.9° 16:15	6.26	74%	82.6°
2039-05-04 Wed	0	—	unknown	—	42.9° 16:10	6.2	83%	94.7°
2039-05-05 Thu	0	—	unknown	—	42.9° 16:05	6.14	91%	107.1°
2039-05-06 Fri	0	—	unknown	—	42.9° 16:00	6.08	96%	119.6°
2039-05-07 Sat	0	—	unknown	—	42.9° 15:55	6.03	100%	131.7°
2039-05-08 Sun	0	—	unknown	—	42.9° 15:55	5.97	100%	142.4°
2039-05-09 Mon	0	—	unknown	—	42.9° 15:50	5.91	97%	149.7°
2039-05-10 Tue	0	—	unknown	—	42.9° 15:45	5.86	91%	151.0°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2039-04-11&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.