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: 12-22 (89), 12-23 (89), 12-24 (89), 12-25 (89), 12-26 (89) — by astronomy; check the weather when the night is within four days.

2025-12-22astronomy score per night — click a bar for that night2026-01-20

night of	astronomy	weather	overall	best window	highest	dark h	Moon	Moon sep.
2025-12-22 Mon	89	0	0	—	42.9° 23:50	11.51	8%	129.9°
2025-12-23 Tue	89	0	0	—	42.9° 23:45	11.51	14%	120.8°
2025-12-24 Wed	89	0	0	—	42.9° 23:45	11.5	21%	110.7°
2025-12-25 Thu	89	0	0	—	42.9° 23:40	11.5	30%	100.2°
2025-12-26 Fri	89	22	19	21:00–22:00 (marginal, 1.0 h)	42.9° 23:35	11.5	41%	89.2°
2025-12-27 Sat	87	100	87	20:40–02:50 (good, 6.17 h)	42.9° 23:30	11.49	51%	77.9°
2025-12-28 Sun	82	79	65	00:00–02:45 (good, 2.75 h)	42.9° 23:25	11.48	62%	66.6°
2025-12-29 Mon	57	100	57	19:55–03:15 (marginal, 7.33 h)	42.9° 23:25	11.48	73%	55.6°
2025-12-30 Tue	36	3	1	—	42.9° 23:20	11.47	83%	45.5°
2025-12-31 Wed	20	44	9	01:00–02:00 (marginal, 1.0 h)	42.9° 23:15	11.46	91%	37.6°
2026-01-01 Thu	12	100	12	—	42.9° 23:10	11.45	97%	33.7°
2026-01-02 Fri	12	76	9	—	42.9° 23:10	11.44	100%	35.5°
2026-01-03 Sat	19	0	0	—	42.9° 23:05	11.43	100%	42.0°
2026-01-04 Sun	33	0	0	—	42.9° 23:00	11.42	97%	51.4°
2026-01-05 Mon	52	7	4	—	42.9° 22:55	11.4	92%	62.0°
2026-01-06 Tue	84	0	0	—	42.9° 22:50	11.39	84%	73.0°
2026-01-07 Wed	88	0	0	—	42.9° 22:50	11.37	76%	83.9°
2026-01-08 Thu	89	60	54	23:00–01:40 (good, 2.67 h)	42.9° 22:45	11.36	67%	94.6°
2026-01-09 Fri	89	43	38	21:00–23:00 (good, 2.0 h)	42.9° 22:40	11.34	57%	104.9°
2026-01-10 Sat	89	40	36	21:00–22:00 (good, 1.0 h)	42.9° 22:35	11.32	47%	114.8°
2026-01-11 Sun	89	0	0	—	42.9° 22:30	11.31	38%	124.0°
2026-01-12 Mon	89	99	88	19:15–01:45 (good, 6.5 h)	42.9° 22:30	11.29	29%	132.3°
2026-01-13 Tue	89	14	12	23:00–00:00 (marginal, 1.0 h)	42.9° 22:25	11.27	21%	139.4°
2026-01-14 Wed	89	100	89	19:10–01:40 (good, 6.5 h)	42.9° 22:20	11.25	14%	144.4°
2026-01-15 Thu	89	87	77	19:00–23:00 (good, 4.0 h)	42.9° 22:15	11.23	8%	146.3°
2026-01-16 Fri	89	0	0	—	42.9° 22:15	11.2	4%	144.6°
2026-01-17 Sat	89	76	67	21:00–00:00 (good, 3.0 h)	42.9° 22:10	11.18	1%	139.6°
2026-01-18 Sun	89	0	0	—	42.9° 22:05	11.16	0%	132.1°
2026-01-19 Mon	89	93	82	20:35–01:10 (good, 4.58 h)	42.9° 22:00	11.13	1%	123.2°
2026-01-20 Tue	89	61	55	19:00–23:00 (good, 4.0 h)	42.9° 21:55	11.11	5%	113.2°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2025-12-22&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.