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: 12-13 (89), 12-14 (89), 12-15 (89), 12-16 (89), 12-17 (89) — by astronomy; check the weather when the night is within four days.

2028-12-13astronomy score per night — click a bar for that night2029-01-11

night of	astronomy	weather	overall	best window	highest	dark h	Moon	Moon sep.
2028-12-13 Wed	89	—	unknown	21:10–03:45 (good, 6.58 h)	42.9° 00:25	11.48	6%	137.4°
2028-12-14 Thu	89	—	unknown	21:05–03:40 (good, 6.58 h)	42.9° 00:20	11.49	2%	145.4°
2028-12-15 Fri	89	—	unknown	21:05–03:35 (good, 6.5 h)	42.9° 00:15	11.49	0%	149.4°
2028-12-16 Sat	89	—	unknown	21:00–03:35 (good, 6.58 h)	42.9° 00:15	11.5	1%	148.1°
2028-12-17 Sun	89	—	unknown	20:55–03:30 (good, 6.58 h)	42.9° 00:10	11.5	4%	142.3°
2028-12-18 Mon	89	—	unknown	20:50–03:25 (good, 6.58 h)	42.9° 00:05	11.51	9%	134.0°
2028-12-19 Tue	89	—	unknown	20:50–03:20 (good, 6.5 h)	42.9° 00:00	11.51	15%	124.5°
2028-12-20 Wed	89	—	unknown	20:45–03:15 (good, 6.5 h)	42.9° 00:00	11.51	23%	114.5°
2028-12-21 Thu	89	—	unknown	20:45–03:15 (good, 6.5 h)	42.9° 23:55	11.51	32%	104.3°
2028-12-22 Fri	89	—	unknown	20:45–03:10 (good, 6.42 h)	42.9° 23:50	11.51	41%	94.1°
2028-12-23 Sat	88	—	unknown	20:50–03:05 (good, 6.25 h)	42.9° 23:45	11.5	50%	83.9°
2028-12-24 Sun	85	—	unknown	21:00–03:00 (good, 6.0 h)	42.9° 23:40	11.5	60%	73.7°
2028-12-25 Mon	75	—	unknown	22:45–02:55 (good, 4.17 h)	42.9° 23:40	11.5	69%	63.7°
2028-12-26 Tue	51	—	unknown	20:15–03:25 (marginal, 7.17 h)	42.9° 23:35	11.49	77%	54.0°
2028-12-27 Wed	34	—	unknown	20:30–03:10 (marginal, 6.67 h)	42.9° 23:30	11.49	85%	44.8°
2028-12-28 Thu	21	—	unknown	23:00–02:45 (marginal, 3.75 h)	42.9° 23:25	11.48	92%	36.9°
2028-12-29 Fri	12	—	unknown	—	42.9° 23:20	11.47	96%	31.6°
2028-12-30 Sat	10	—	unknown	—	42.9° 23:20	11.47	99%	30.7°
2028-12-31 Sun	14	—	unknown	20:25–21:00 (marginal, 0.58 h)	42.9° 23:15	11.46	100%	34.9°
2029-01-01 Mon	24	—	unknown	19:45–00:20 (marginal, 4.58 h)	42.9° 23:10	11.45	98%	42.9°
2029-01-02 Tue	41	—	unknown	19:25–02:10 (marginal, 6.75 h)	42.9° 23:05	11.44	94%	53.1°
2029-01-03 Wed	81	—	unknown	19:50–22:20 (good, 2.5 h)	42.9° 23:05	11.42	87%	64.6°
2029-01-04 Thu	87	—	unknown	19:45–01:00 (good, 5.25 h)	42.9° 23:00	11.41	78%	76.6°
2029-01-05 Fri	89	—	unknown	19:40–01:50 (good, 6.17 h)	42.9° 22:55	11.4	68%	88.8°
2029-01-06 Sat	89	—	unknown	19:35–02:00 (good, 6.42 h)	42.9° 22:50	11.38	57%	101.1°
2029-01-07 Sun	89	—	unknown	19:35–02:00 (good, 6.42 h)	42.9° 22:45	11.37	46%	113.0°
2029-01-08 Mon	89	—	unknown	19:30–02:00 (good, 6.5 h)	42.9° 22:45	11.35	35%	124.4°
2029-01-09 Tue	89	—	unknown	19:25–02:00 (good, 6.58 h)	42.9° 22:40	11.34	24%	134.8°
2029-01-10 Wed	89	—	unknown	19:20–01:55 (good, 6.58 h)	42.9° 22:35	11.32	16%	143.4°
2029-01-11 Thu	89	—	unknown	19:15–01:50 (good, 6.58 h)	42.9° 22:30	11.3	8%	148.7°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2028-12-13&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.