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: 12-20 (89), 12-21 (89), 12-22 (89), 12-23 (89), 12-24 (89) — by astronomy; check the weather when the night is within four days.

2027-12-20astronomy score per night — click a bar for that night2028-01-18

night of	astronomy	weather	overall	best window	highest	dark h	Moon	Moon sep.
2027-12-20 Mon	89	—	unknown	20:45–03:10 (good, 6.42 h)	42.9° 00:00	11.51	44%	98.9°
2027-12-21 Tue	89	—	unknown	20:45–03:10 (good, 6.42 h)	42.9° 23:55	11.51	33%	110.3°
2027-12-22 Wed	89	—	unknown	20:40–03:10 (good, 6.5 h)	42.9° 23:55	11.51	24%	121.2°
2027-12-23 Thu	89	—	unknown	20:35–03:10 (good, 6.58 h)	42.9° 23:50	11.51	15%	131.1°
2027-12-24 Fri	89	—	unknown	20:30–03:05 (good, 6.58 h)	42.9° 23:45	11.5	8%	139.6°
2027-12-25 Sat	89	—	unknown	20:25–03:00 (good, 6.58 h)	42.9° 23:40	11.5	4%	145.6°
2027-12-26 Sun	89	—	unknown	20:25–02:55 (good, 6.5 h)	42.9° 23:35	11.5	1%	148.1°
2027-12-27 Mon	89	—	unknown	20:20–02:50 (good, 6.5 h)	42.9° 23:35	11.49	0%	146.3°
2027-12-28 Tue	89	—	unknown	20:15–02:50 (good, 6.58 h)	42.9° 23:30	11.49	1%	141.0°
2027-12-29 Wed	89	—	unknown	20:10–02:45 (good, 6.58 h)	42.9° 23:25	11.48	4%	133.6°
2027-12-30 Thu	89	—	unknown	20:05–02:40 (good, 6.58 h)	42.9° 23:20	11.47	9%	124.9°
2027-12-31 Fri	89	—	unknown	20:05–02:35 (good, 6.5 h)	42.9° 23:15	11.46	15%	115.5°
2028-01-01 Sat	89	—	unknown	20:05–02:35 (good, 6.5 h)	42.9° 23:15	11.45	22%	105.8°
2028-01-02 Sun	89	—	unknown	20:05–02:30 (good, 6.42 h)	42.9° 23:10	11.44	30%	95.8°
2028-01-03 Mon	88	—	unknown	20:05–02:25 (good, 6.33 h)	42.9° 23:05	11.43	39%	85.7°
2028-01-04 Tue	86	—	unknown	20:10–02:20 (good, 6.17 h)	42.9° 23:00	11.42	49%	75.5°
2028-01-05 Wed	80	—	unknown	21:00–02:15 (good, 5.25 h)	42.9° 23:00	11.41	58%	65.2°
2028-01-06 Thu	59	—	unknown	00:15–01:25 (good, 1.17 h)	42.9° 22:55	11.4	68%	55.2°
2028-01-07 Fri	40	—	unknown	19:40–02:35 (marginal, 6.92 h)	42.9° 22:50	11.38	78%	45.7°
2028-01-08 Sat	24	—	unknown	20:05–02:10 (marginal, 6.08 h)	42.9° 22:45	11.37	86%	37.6°
2028-01-09 Sun	14	—	unknown	—	42.9° 22:40	11.35	93%	32.6°
2028-01-10 Mon	11	—	unknown	—	42.9° 22:40	11.33	98%	32.7°
2028-01-11 Tue	17	—	unknown	19:35–21:20 (marginal, 1.75 h)	42.9° 22:35	11.31	100%	38.4°
2028-01-12 Wed	28	—	unknown	19:00–00:40 (marginal, 5.67 h)	42.9° 22:30	11.3	99%	47.7°
2028-01-13 Thu	48	—	unknown	18:55–01:40 (marginal, 6.75 h)	42.9° 22:25	11.28	95%	59.0°
2028-01-14 Fri	84	—	unknown	19:10–22:50 (good, 3.67 h)	42.9° 22:20	11.26	89%	71.2°
2028-01-15 Sat	88	—	unknown	19:05–00:55 (good, 5.83 h)	42.9° 22:20	11.24	80%	83.6°
2028-01-16 Sun	89	—	unknown	19:00–01:15 (good, 6.25 h)	42.9° 22:15	11.21	70%	95.8°
2028-01-17 Mon	89	—	unknown	19:00–01:20 (good, 6.33 h)	42.9° 22:10	11.19	60%	107.6°
2028-01-18 Tue	89	—	unknown	19:00–01:25 (good, 6.42 h)	42.9° 22:05	11.17	49%	118.8°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2027-12-20&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.