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: 04-02 (9), 04-03 (7), 04-04 (6), 04-05 (5), 04-06 (4) — by astronomy; check the weather when the night is within four days.

2040-04-02astronomy score per night — click a bar for that night2040-05-01

night of	astronomy	weather	overall	best window	highest	dark h	Moon	Moon sep.
2040-04-02 Mon	9	—	unknown	21:25–21:30 (good, 0.08 h)	42.9° 18:10	7.99	68%	149.8°
2040-04-03 Tue	7	—	unknown	21:30–22:00 (marginal, 0.5 h)	42.9° 18:10	7.94	57%	146.2°
2040-04-04 Wed	6	—	unknown	21:30–21:55 (marginal, 0.42 h)	42.9° 18:05	7.88	46%	138.4°
2040-04-05 Thu	5	—	unknown	21:30–21:50 (marginal, 0.33 h)	42.9° 18:00	7.83	35%	128.3°
2040-04-06 Fri	4	—	unknown	21:30–21:45 (marginal, 0.25 h)	42.9° 17:55	7.77	24%	117.0°
2040-04-07 Sat	3	—	unknown	21:00–21:10 (marginal, 0.17 h)	42.9° 17:50	7.72	16%	105.2°
2040-04-08 Sun	3	—	unknown	21:00–21:10 (marginal, 0.17 h)	42.9° 17:50	7.66	8%	93.3°
2040-04-09 Mon	2	—	unknown	21:00–21:05 (marginal, 0.08 h)	42.9° 17:45	7.6	3%	81.5°
2040-04-10 Tue	1	—	unknown	—	42.9° 17:40	7.55	1%	70.0°
2040-04-11 Wed	1	—	unknown	—	42.9° 17:35	7.49	0%	59.1°
2040-04-12 Thu	1	—	unknown	—	42.9° 17:35	7.43	2%	48.9°
2040-04-13 Fri	1	—	unknown	—	42.9° 17:30	7.37	6%	40.2°
2040-04-14 Sat	0	—	unknown	—	42.9° 17:25	7.32	11%	33.6°
2040-04-15 Sun	0	—	unknown	—	42.9° 17:20	7.26	18%	30.4°
2040-04-16 Mon	0	—	unknown	—	42.9° 17:15	7.2	26%	31.4°
2040-04-17 Tue	0	—	unknown	—	42.9° 17:15	7.14	35%	36.0°
2040-04-18 Wed	0	—	unknown	—	42.9° 17:10	7.08	44%	43.2°
2040-04-19 Thu	0	—	unknown	—	42.9° 17:05	7.03	54%	51.8°
2040-04-20 Fri	0	—	unknown	—	42.9° 17:00	6.97	63%	61.4°
2040-04-21 Sat	0	—	unknown	—	42.9° 16:55	6.91	72%	71.6°
2040-04-22 Sun	0	—	unknown	—	42.9° 16:55	6.85	81%	82.3°
2040-04-23 Mon	0	—	unknown	—	42.9° 16:50	6.79	88%	93.4°
2040-04-24 Tue	0	—	unknown	—	42.9° 16:45	6.74	94%	104.7°
2040-04-25 Wed	0	—	unknown	—	42.9° 16:40	6.68	98%	116.2°
2040-04-26 Thu	0	—	unknown	—	42.9° 16:40	6.62	100%	127.4°
2040-04-27 Fri	0	—	unknown	—	42.9° 16:35	6.56	99%	137.7°
2040-04-28 Sat	0	—	unknown	—	42.9° 16:30	6.5	96%	145.8°
2040-04-29 Sun	0	—	unknown	—	42.9° 16:25	6.44	90%	149.7°
2040-04-30 Mon	0	—	unknown	—	42.9° 16:20	6.39	81%	147.5°
2040-05-01 Tue	0	—	unknown	—	42.9° 16:20	6.33	71%	140.4°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2040-04-02&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.