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: 01-12 (89), 01-13 (89), 01-14 (89), 01-15 (89), 01-16 (89) — by astronomy; check the weather when the night is within four days.

2026-01-12astronomy score per night — click a bar for that night2026-02-10

night of	astronomy	weather	overall	best window	highest	dark h	Moon	Moon sep.
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°
2026-01-21 Wed	89	0	0	—	42.9° 21:55	11.08	10%	102.6°
2026-01-22 Thu	89	0	0	—	42.9° 21:50	11.06	17%	91.7°
2026-01-23 Fri	88	41	36	19:05–21:00 (good, 1.92 h)	42.9° 21:45	11.03	26%	80.5°
2026-01-24 Sat	84	6	5	—	42.9° 21:40	11.0	36%	69.3°
2026-01-25 Sun	70	0	0	—	42.9° 21:35	10.97	47%	58.5°
2026-01-26 Mon	55	0	0	—	42.9° 21:35	10.94	58%	48.4°
2026-01-27 Tue	36	11	4	—	42.9° 21:30	10.91	69%	39.9°
2026-01-28 Wed	21	0	0	—	42.9° 21:25	10.88	80%	34.6°
2026-01-29 Thu	14	0	0	—	42.9° 21:20	10.85	88%	34.2°
2026-01-30 Fri	15	0	0	—	42.9° 21:15	10.82	95%	38.9°
2026-01-31 Sat	20	0	0	—	42.9° 21:15	10.79	99%	47.2°
2026-02-01 Sun	30	0	0	—	42.9° 21:10	10.76	100%	57.3°
2026-02-02 Mon	44	0	0	—	42.9° 21:05	10.72	99%	68.2°
2026-02-03 Tue	77	7	6	18:45–19:00 (marginal, 0.25 h)	42.9° 21:00	10.69	95%	79.3°
2026-02-04 Wed	89	0	0	—	42.9° 21:00	10.66	89%	90.3°
2026-02-05 Thu	89	0	0	—	42.9° 20:55	10.62	82%	101.0°
2026-02-06 Fri	89	0	0	—	42.9° 20:50	10.59	74%	111.2°
2026-02-07 Sat	89	81	72	19:20–23:00 (good, 3.67 h)	42.9° 20:45	10.55	65%	120.8°
2026-02-08 Sun	89	37	33	21:00–22:00 (marginal, 1.0 h)	42.9° 20:40	10.51	56%	129.6°
2026-02-09 Mon	89	0	0	—	42.9° 20:40	10.48	46%	137.2°
2026-02-10 Tue	89	0	0	—	42.9° 20:35	10.44	37%	143.0°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2026-01-12&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.