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: 01-25 (89), 01-26 (89), 01-27 (89), 01-28 (89), 01-29 (89) — by astronomy; check the weather when the night is within four days.

2027-01-15astronomy score per night — click a bar for that night2027-02-13

night of	astronomy	weather	overall	best window	highest	dark h	Moon	Moon sep.
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°
2027-01-20 Wed	13	—	unknown	19:15–19:20 (marginal, 0.08 h)	42.9° 22:00	11.11	96%	35.4°
2027-01-21 Thu	19	—	unknown	19:00–22:05 (marginal, 3.08 h)	42.9° 21:55	11.09	100%	42.7°
2027-01-22 Fri	31	—	unknown	19:05–00:40 (marginal, 5.58 h)	42.9° 21:50	11.06	100%	52.9°
2027-01-23 Sat	48	—	unknown	19:05–01:05 (marginal, 6.0 h)	42.9° 21:45	11.04	97%	64.4°
2027-01-24 Sun	85	—	unknown	19:05–22:45 (good, 3.67 h)	42.9° 21:40	11.01	92%	76.4°
2027-01-25 Mon	89	—	unknown	19:05–00:25 (good, 5.33 h)	42.9° 21:40	10.98	84%	88.4°
2027-01-26 Tue	89	—	unknown	19:05–00:35 (good, 5.5 h)	42.9° 21:35	10.95	75%	99.9°
2027-01-27 Wed	89	—	unknown	19:10–00:40 (good, 5.5 h)	42.9° 21:30	10.92	65%	110.9°
2027-01-28 Thu	89	—	unknown	19:10–00:45 (good, 5.58 h)	42.9° 21:25	10.89	55%	121.2°
2027-01-29 Fri	89	—	unknown	19:10–00:40 (good, 5.5 h)	42.9° 21:20	10.86	45%	130.4°
2027-01-30 Sat	89	—	unknown	19:10–00:40 (good, 5.5 h)	42.9° 21:20	10.83	36%	138.2°
2027-01-31 Sun	89	—	unknown	19:15–00:35 (good, 5.33 h)	42.9° 21:15	10.8	27%	144.0°
2027-02-01 Mon	89	—	unknown	19:15–00:30 (good, 5.25 h)	42.9° 21:10	10.77	19%	146.8°
2027-02-02 Tue	89	—	unknown	19:15–00:25 (good, 5.17 h)	42.9° 21:05	10.73	12%	145.9°
2027-02-03 Wed	89	—	unknown	19:15–00:20 (good, 5.08 h)	42.9° 21:05	10.7	7%	141.7°
2027-02-04 Thu	89	—	unknown	19:15–00:20 (good, 5.08 h)	42.9° 21:00	10.66	3%	135.1°
2027-02-05 Fri	89	—	unknown	19:20–00:15 (good, 4.92 h)	42.9° 20:55	10.63	0%	126.9°
2027-02-06 Sat	89	—	unknown	19:20–00:10 (good, 4.83 h)	42.9° 20:50	10.59	0%	117.8°
2027-02-07 Sun	89	—	unknown	19:20–00:05 (good, 4.75 h)	42.9° 20:45	10.56	2%	108.0°
2027-02-08 Mon	89	—	unknown	19:20–00:00 (good, 4.67 h)	42.9° 20:45	10.52	5%	97.8°
2027-02-09 Tue	89	—	unknown	19:25–00:00 (good, 4.58 h)	42.9° 20:40	10.49	10%	87.4°
2027-02-10 Wed	87	—	unknown	19:25–23:55 (good, 4.5 h)	42.9° 20:35	10.45	17%	76.8°
2027-02-11 Thu	81	—	unknown	19:25–23:50 (good, 4.42 h)	42.9° 20:30	10.41	25%	66.3°
2027-02-12 Fri	66	—	unknown	19:25–23:35 (good, 4.17 h)	42.9° 20:25	10.37	35%	56.0°
2027-02-13 Sat	51	—	unknown	19:25–23:15 (good, 3.83 h)	42.9° 20:25	10.33	46%	46.5°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2027-01-15&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.