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

2031-04-13astronomy score per night — click a bar for that night2031-05-12

night of	astronomy	weather	overall	best window	highest	dark h	Moon	Moon sep.
2031-04-13 Sun	1	—	unknown	—	42.9° 17:30	7.42	57%	147.1°
2031-04-14 Mon	1	—	unknown	—	42.9° 17:30	7.36	46%	137.5°
2031-04-15 Tue	0	—	unknown	—	42.9° 17:25	7.31	34%	126.4°
2031-04-16 Wed	0	—	unknown	—	42.9° 17:20	7.25	24%	114.6°
2031-04-17 Thu	0	—	unknown	—	42.9° 17:15	7.19	16%	102.5°
2031-04-18 Fri	0	—	unknown	—	42.9° 17:10	7.13	8%	90.4°
2031-04-19 Sat	0	—	unknown	—	42.9° 17:10	7.07	4%	78.6°
2031-04-20 Sun	0	—	unknown	—	42.9° 17:05	7.02	1%	67.0°
2031-04-21 Mon	0	—	unknown	—	42.9° 17:00	6.96	0%	55.9°
2031-04-22 Tue	0	—	unknown	—	42.9° 16:55	6.9	2%	45.6°
2031-04-23 Wed	0	—	unknown	—	42.9° 16:50	6.84	5%	36.6°
2031-04-24 Thu	0	—	unknown	—	42.9° 16:50	6.78	10%	29.7°
2031-04-25 Fri	0	—	unknown	—	42.9° 16:45	6.72	16%	26.4°
2031-04-26 Sat	0	—	unknown	—	42.9° 16:40	6.67	24%	28.0°
2031-04-27 Sun	0	—	unknown	—	42.9° 16:35	6.61	32%	33.6°
2031-04-28 Mon	0	—	unknown	—	42.9° 16:35	6.55	42%	41.6°
2031-04-29 Tue	0	—	unknown	—	42.9° 16:30	6.49	51%	51.0°
2031-04-30 Wed	0	—	unknown	—	42.9° 16:25	6.43	61%	61.3°
2031-05-01 Thu	0	—	unknown	—	42.9° 16:20	6.38	70%	72.1°
2031-05-02 Fri	0	—	unknown	—	42.9° 16:15	6.32	79%	83.4°
2031-05-03 Sat	0	—	unknown	—	42.9° 16:15	6.26	87%	95.2°
2031-05-04 Sun	0	—	unknown	—	42.9° 16:10	6.2	94%	107.3°
2031-05-05 Mon	0	—	unknown	—	42.9° 16:05	6.14	98%	119.5°
2031-05-06 Tue	0	—	unknown	—	42.9° 16:00	6.09	100%	131.5°
2031-05-07 Wed	0	—	unknown	—	42.9° 15:55	6.03	99%	142.5°
2031-05-08 Thu	0	—	unknown	—	42.9° 15:55	5.97	96%	150.8°
2031-05-09 Fri	0	—	unknown	—	42.9° 15:50	5.92	89%	153.6°
2031-05-10 Sat	0	—	unknown	—	42.9° 15:45	5.86	81%	149.3°
2031-05-11 Sun	0	—	unknown	—	42.9° 15:40	5.81	71%	140.2°
2031-05-12 Mon	0	—	unknown	—	42.9° 15:40	5.75	60%	129.1°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2031-04-13&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.