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: 02-04 (89), 02-05 (89), 02-06 (89), 02-07 (89), 02-08 (89) — by astronomy; check the weather when the night is within four days.

2026-01-23astronomy score per night — click a bar for that night2026-02-21

night of	astronomy	weather	overall	best window	highest	dark h	Moon	Moon sep.
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°
2026-02-11 Wed	89	0	0	—	42.9° 20:30	10.4	28%	146.0°
2026-02-12 Thu	89	0	0	—	42.9° 20:25	10.36	20%	145.5°
2026-02-13 Fri	89	0	0	—	42.9° 20:20	10.32	13%	141.5°
2026-02-14 Sat	89	17	15	23:00–23:55 (marginal, 0.92 h)	42.9° 20:20	10.29	7%	134.8°
2026-02-15 Sun	88	0	0	—	42.9° 20:15	10.25	3%	126.2°
2026-02-16 Mon	86	12	11	19:30–20:00 (marginal, 0.5 h)	42.9° 20:10	10.21	0%	116.4°
2026-02-17 Tue	85	0	0	—	42.9° 20:05	10.17	0%	105.8°
2026-02-18 Wed	83	97	80	19:35–23:20 (good, 3.75 h)	42.9° 20:05	10.12	2%	94.7°
2026-02-19 Thu	81	0	0	—	42.9° 20:00	10.08	7%	83.4°
2026-02-20 Fri	75	0	0	—	42.9° 19:55	10.04	14%	72.0°
2026-02-21 Sat	66	0	0	—	42.9° 19:50	10.0	22%	60.9°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2026-01-23&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.