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.

2025-10-14astronomy score per night — click a bar for that night2025-11-12

night of	astronomy	weather	overall	best window	highest	dark h	Moon	Moon sep.
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°
2025-10-26 Sun	89	12	10	04:00–05:00 (marginal, 1.0 h)	42.9° 03:35	10.29	24%	145.1°
2025-10-27 Mon	89	35	31	00:20–01:00 (good, 0.67 h)	42.9° 03:30	10.32	33%	140.8°
2025-10-28 Tue	89	100	89	00:15–05:20 (good, 5.08 h)	42.9° 03:25	10.36	42%	133.9°
2025-10-29 Wed	89	100	89	00:10–05:20 (good, 5.17 h)	42.9° 03:25	10.4	52%	125.2°
2025-10-30 Thu	89	31	28	00:10–02:00 (good, 1.83 h)	42.9° 03:20	10.44	63%	115.3°
2025-10-31 Fri	89	65	58	00:15–02:00 (good, 1.75 h)	42.9° 03:15	10.47	73%	104.6°
2025-11-01 Sat	89	99	88	00:25–05:25 (good, 5.0 h)	42.9° 03:10	10.51	82%	93.1°
2025-11-02 Sun	87	95	83	01:35–05:25 (good, 3.83 h)	42.9° 03:05	10.55	90%	81.2°
2025-11-03 Mon	71	0	0	—	42.9° 03:05	10.58	96%	69.1°
2025-11-04 Tue	35	0	0	—	42.9° 03:00	10.62	99%	57.4°
2025-11-05 Wed	22	0	0	—	42.9° 02:55	10.65	100%	46.6°
2025-11-06 Thu	15	0	0	—	42.9° 02:50	10.69	97%	38.2°
2025-11-07 Fri	13	0	0	—	42.9° 02:50	10.72	92%	33.9°
2025-11-08 Sat	20	0	0	—	42.9° 02:45	10.75	84%	35.2°
2025-11-09 Sun	34	0	0	—	42.9° 02:40	10.78	74%	41.2°
2025-11-10 Mon	53	0	0	—	42.9° 02:35	10.82	64%	49.8°
2025-11-11 Tue	68	100	68	23:40–04:30 (good, 4.83 h)	42.9° 02:30	10.85	53%	59.7°
2025-11-12 Wed	83	99	83	23:15–05:20 (good, 6.08 h)	42.9° 02:30	10.88	43%	69.9°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2025-10-14&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.