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: 10-18 (89), 10-19 (89), 10-20 (89), 10-21 (89), 10-22 (89) — by astronomy; check the weather when the night is within four days.

2025-09-26astronomy score per night — click a bar for that night2025-10-25

night of	astronomy	weather	overall	best window	highest	dark h	Moon	Moon sep.
2025-09-26 Fri	55	6	3	—	42.9° 06:35	8.95	22%	139.9°
2025-09-27 Sat	57	0	0	—	42.9° 06:30	9.0	31%	144.5°
2025-09-28 Sun	59	0	0	—	42.9° 06:25	9.05	40%	146.1°
2025-09-29 Mon	60	12	7	—	42.9° 06:20	9.09	49%	144.0°
2025-09-30 Tue	63	96	61	03:05–05:50 (good, 2.75 h)	42.9° 06:15	9.14	59%	138.7°
2025-10-01 Wed	64	0	0	—	42.9° 06:15	9.19	69%	130.9°
2025-10-02 Thu	66	0	0	—	42.9° 06:10	9.24	78%	121.6°
2025-10-03 Fri	65	0	0	—	42.9° 06:05	9.29	86%	111.0°
2025-10-04 Sat	61	100	61	03:10–05:50 (good, 2.67 h)	42.9° 06:00	9.33	93%	99.7°
2025-10-05 Sun	43	3	1	—	42.9° 05:55	9.38	98%	87.7°
2025-10-06 Mon	32	0	0	—	42.9° 05:55	9.43	100%	75.6°
2025-10-07 Tue	22	0	0	—	42.9° 05:50	9.47	99%	63.6°
2025-10-08 Wed	16	0	0	—	42.9° 05:45	9.52	95%	52.3°
2025-10-09 Thu	13	94	12	05:00–06:00 (marginal, 1.0 h)	42.9° 05:40	9.57	89%	42.6°
2025-10-10 Fri	13	10	1	—	42.9° 05:40	9.61	80%	35.9°
2025-10-11 Sat	18	4	1	—	42.9° 05:35	9.66	70%	33.9°
2025-10-12 Sun	28	52	15	02:00–04:00 (marginal, 2.0 h)	42.9° 05:30	9.7	59%	37.0°
2025-10-13 Mon	42	1	0	—	42.9° 05:25	9.74	48%	43.7°
2025-10-14 Tue	56	0	0	—	42.9° 05:20	9.79	38%	52.5°
2025-10-15 Wed	69	15	11	05:00–06:05 (marginal, 1.08 h)	42.9° 05:20	9.83	28%	62.3°
2025-10-16 Thu	81	0	0	—	42.9° 05:15	9.87	19%	72.5°
2025-10-17 Fri	88	0	0	—	42.9° 05:10	9.92	12%	82.8°
2025-10-18 Sat	89	4	3	06:00–06:10 (marginal, 0.17 h)	42.9° 05:05	9.96	6%	93.1°
2025-10-19 Sun	89	0	0	—	42.9° 05:00	10.0	2%	103.2°
2025-10-20 Mon	89	0	0	—	42.9° 05:00	10.04	0%	113.0°
2025-10-21 Tue	89	0	0	—	42.9° 04:55	10.08	0%	122.3°
2025-10-22 Wed	89	0	0	—	42.9° 04:50	10.13	2%	130.8°
2025-10-23 Thu	89	2	2	—	42.9° 04:45	10.17	5%	138.2°
2025-10-24 Fri	89	83	74	01:50–06:00 (good, 4.17 h)	42.9° 04:45	10.21	10%	143.6°
2025-10-25 Sat	89	23	21	01:20–03:00 (marginal, 1.67 h)	42.9° 03:40	10.25	17%	146.1°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2025-09-26&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.