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: 12-29 (89), 12-30 (89), 12-31 (89), 01-01 (89), 01-02 (89) — by astronomy; check the weather when the night is within four days.

2026-12-21astronomy score per night — click a bar for that night2027-01-19

night of	astronomy	weather	overall	best window	highest	dark h	Moon	Moon sep.
2026-12-21 Mon	22	—	unknown	22:55–03:15 (marginal, 4.33 h)	42.9° 23:55	11.51	93%	40.4°
2026-12-22 Tue	12	—	unknown	—	42.9° 23:50	11.51	98%	34.3°
2026-12-23 Wed	10	—	unknown	—	42.9° 23:50	11.51	100%	33.4°
2026-12-24 Thu	16	—	unknown	20:45–22:25 (marginal, 1.67 h)	42.9° 23:45	11.5	99%	38.4°
2026-12-25 Fri	30	—	unknown	20:10–02:25 (marginal, 6.25 h)	42.9° 23:40	11.5	95%	47.3°
2026-12-26 Sat	49	—	unknown	19:50–02:55 (marginal, 7.08 h)	42.9° 23:35	11.5	88%	58.1°
2026-12-27 Sun	83	—	unknown	20:20–00:25 (good, 4.08 h)	42.9° 23:30	11.49	79%	69.7°
2026-12-28 Mon	87	—	unknown	20:15–02:15 (good, 6.0 h)	42.9° 23:30	11.49	70%	81.3°
2026-12-29 Tue	89	—	unknown	20:10–02:25 (good, 6.25 h)	42.9° 23:25	11.48	59%	92.7°
2026-12-30 Wed	89	—	unknown	20:05–02:30 (good, 6.42 h)	42.9° 23:20	11.47	48%	103.7°
2026-12-31 Thu	89	—	unknown	20:00–02:30 (good, 6.5 h)	42.9° 23:15	11.46	38%	114.2°
2027-01-01 Fri	89	—	unknown	20:00–02:30 (good, 6.5 h)	42.9° 23:10	11.45	29%	123.9°
2027-01-02 Sat	89	—	unknown	19:55–02:30 (good, 6.58 h)	42.9° 23:10	11.44	20%	132.7°
2027-01-03 Sun	89	—	unknown	19:50–02:25 (good, 6.58 h)	42.9° 23:05	11.43	13%	140.0°
2027-01-04 Mon	89	—	unknown	19:45–02:20 (good, 6.58 h)	42.9° 23:00	11.42	8%	145.1°
2027-01-05 Tue	89	—	unknown	19:45–02:15 (good, 6.5 h)	42.9° 22:55	11.41	3%	147.0°
2027-01-06 Wed	89	—	unknown	19:40–02:10 (good, 6.5 h)	42.9° 22:55	11.39	1%	145.2°
2027-01-07 Thu	89	—	unknown	19:35–02:10 (good, 6.58 h)	42.9° 22:50	11.38	0%	140.2°
2027-01-08 Fri	89	—	unknown	19:30–02:05 (good, 6.58 h)	42.9° 22:45	11.36	1%	133.1°
2027-01-09 Sat	89	—	unknown	19:25–02:00 (good, 6.58 h)	42.9° 22:40	11.35	4%	124.7°
2027-01-10 Sun	89	—	unknown	19:25–01:55 (good, 6.5 h)	42.9° 22:35	11.33	8%	115.4°
2027-01-11 Mon	89	—	unknown	19:20–01:50 (good, 6.5 h)	42.9° 22:35	11.31	14%	105.6°
2027-01-12 Tue	89	—	unknown	19:20–01:50 (good, 6.5 h)	42.9° 22:30	11.29	22%	95.4°
2027-01-13 Wed	88	—	unknown	19:20–01:45 (good, 6.42 h)	42.9° 22:25	11.27	31%	84.9°
2027-01-14 Thu	86	—	unknown	19:25–01:40 (good, 6.25 h)	42.9° 22:20	11.25	40%	74.3°
2027-01-15 Fri	77	—	unknown	19:45–01:35 (good, 5.83 h)	42.9° 22:15	11.23	51%	63.7°
2027-01-16 Sat	62	—	unknown	22:20–01:00 (good, 2.67 h)	42.9° 22:15	11.21	62%	53.4°
2027-01-17 Sun	41	—	unknown	19:00–01:55 (marginal, 6.92 h)	42.9° 22:10	11.19	72%	43.9°
2027-01-18 Mon	25	—	unknown	19:15–01:30 (marginal, 6.25 h)	42.9° 22:05	11.16	82%	36.5°
2027-01-19 Tue	14	—	unknown	—	42.9° 22:00	11.14	90%	33.1°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2026-12-21&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.