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: 01-20 (89), 01-21 (89), 02-03 (89), 02-04 (89), 02-05 (89) — by astronomy; check the weather when the night is within four days.

2037-01-20astronomy score per night — click a bar for that night2037-02-18

night of	astronomy	weather	overall	best window	highest	dark h	Moon	Moon sep.
2037-01-20 Tue	89	—	unknown	19:00–01:15 (good, 6.25 h)	42.9° 21:55	11.1	17%	90.5°
2037-01-21 Wed	89	—	unknown	19:05–01:10 (good, 6.08 h)	42.9° 21:50	11.07	25%	79.8°
2037-01-22 Thu	86	—	unknown	19:05–01:05 (good, 6.0 h)	42.9° 21:50	11.05	34%	69.0°
2037-01-23 Fri	82	—	unknown	19:05–01:05 (good, 6.0 h)	42.9° 21:45	11.02	43%	58.3°
2037-01-24 Sat	65	—	unknown	20:35–00:35 (good, 4.0 h)	42.9° 21:40	10.99	53%	47.8°
2037-01-25 Sun	46	—	unknown	19:05–01:25 (marginal, 6.33 h)	42.9° 21:35	10.96	63%	37.8°
2037-01-26 Mon	29	—	unknown	19:10–01:05 (marginal, 5.92 h)	42.9° 21:30	10.93	73%	29.4°
2037-01-27 Tue	19	—	unknown	19:10–00:40 (marginal, 5.5 h)	42.9° 21:30	10.9	82%	25.0°
2037-01-28 Wed	13	—	unknown	—	42.9° 21:25	10.87	90%	27.3°
2037-01-29 Thu	14	—	unknown	19:10–20:30 (marginal, 1.33 h)	42.9° 21:20	10.84	96%	35.5°
2037-01-30 Fri	22	—	unknown	19:10–23:10 (marginal, 4.0 h)	42.9° 21:15	10.81	99%	46.9°
2037-01-31 Sat	34	—	unknown	19:15–00:20 (marginal, 5.08 h)	42.9° 21:15	10.78	100%	59.8°
2037-02-01 Sun	51	—	unknown	19:15–20:55 (good, 1.67 h)	42.9° 21:10	10.75	97%	73.3°
2037-02-02 Mon	86	—	unknown	19:15–23:15 (good, 4.0 h)	42.9° 21:05	10.71	92%	87.0°
2037-02-03 Tue	89	—	unknown	19:15–00:00 (good, 4.75 h)	42.9° 21:00	10.68	84%	100.4°
2037-02-04 Wed	89	—	unknown	19:20–00:05 (good, 4.75 h)	42.9° 20:55	10.64	74%	113.4°
2037-02-05 Thu	89	—	unknown	19:20–00:05 (good, 4.75 h)	42.9° 20:55	10.61	64%	125.7°
2037-02-06 Fri	89	—	unknown	19:20–00:10 (good, 4.83 h)	42.9° 20:50	10.57	53%	136.9°
2037-02-07 Sat	89	—	unknown	19:20–00:05 (good, 4.75 h)	42.9° 20:45	10.54	43%	146.5°
2037-02-08 Sun	89	—	unknown	19:20–00:00 (good, 4.67 h)	42.9° 20:40	10.5	33%	153.2°
2037-02-09 Mon	89	—	unknown	19:25–23:55 (good, 4.5 h)	42.9° 20:35	10.46	24%	155.0°
2037-02-10 Tue	89	—	unknown	19:25–23:55 (good, 4.5 h)	42.9° 20:35	10.43	16%	151.4°
2037-02-11 Wed	89	—	unknown	19:25–23:50 (good, 4.42 h)	42.9° 20:30	10.39	9%	144.1°
2037-02-12 Thu	89	—	unknown	19:25–23:45 (good, 4.33 h)	42.9° 20:25	10.35	4%	135.0°
2037-02-13 Fri	89	—	unknown	19:30–23:40 (good, 4.17 h)	42.9° 20:20	10.31	1%	125.0°
2037-02-14 Sat	89	—	unknown	19:30–23:35 (good, 4.08 h)	42.9° 20:20	10.27	0%	114.6°
2037-02-15 Sun	88	—	unknown	19:30–23:35 (good, 4.08 h)	42.9° 20:15	10.23	0%	104.0°
2037-02-16 Mon	86	—	unknown	19:30–23:30 (good, 4.0 h)	42.9° 20:10	10.19	3%	93.3°
2037-02-17 Tue	84	—	unknown	19:35–23:25 (good, 3.83 h)	42.9° 20:05	10.15	7%	82.6°
2037-02-18 Wed	80	—	unknown	19:35–23:20 (good, 3.75 h)	42.9° 20:00	10.11	12%	71.9°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2037-01-20&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.