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: 02-02 (89), 02-03 (89), 02-04 (89), 02-05 (89), 02-06 (89) — by astronomy; check the weather when the night is within four days.

2040-01-27astronomy score per night — click a bar for that night2040-02-25

night of	astronomy	weather	overall	best window	highest	dark h	Moon	Moon sep.
2040-01-27 Fri	18	—	unknown	19:10–21:55 (marginal, 2.75 h)	42.9° 21:30	10.93	98%	42.6°
2040-01-28 Sat	25	—	unknown	19:10–00:05 (marginal, 4.92 h)	42.9° 21:30	10.9	100%	51.4°
2040-01-29 Sun	36	—	unknown	19:10–00:30 (marginal, 5.33 h)	42.9° 21:25	10.87	100%	61.2°
2040-01-30 Mon	50	—	unknown	19:10–20:10 (good, 1.0 h)	42.9° 21:20	10.83	97%	71.5°
2040-01-31 Tue	82	—	unknown	19:15–22:45 (good, 3.5 h)	42.9° 21:15	10.8	93%	82.2°
2040-02-01 Wed	88	—	unknown	19:15–00:00 (good, 4.75 h)	42.9° 21:10	10.77	88%	93.2°
2040-02-02 Thu	89	—	unknown	19:15–00:10 (good, 4.92 h)	42.9° 21:10	10.74	80%	104.3°
2040-02-03 Fri	89	—	unknown	19:15–00:15 (good, 5.0 h)	42.9° 21:05	10.7	71%	115.4°
2040-02-04 Sat	89	—	unknown	19:15–00:15 (good, 5.0 h)	42.9° 21:00	10.67	61%	126.2°
2040-02-05 Sun	89	—	unknown	19:20–00:15 (good, 4.92 h)	42.9° 20:55	10.64	50%	136.4°
2040-02-06 Mon	89	—	unknown	19:20–00:10 (good, 4.83 h)	42.9° 20:50	10.6	39%	144.9°
2040-02-07 Tue	89	—	unknown	19:20–00:05 (good, 4.75 h)	42.9° 20:50	10.56	28%	149.9°
2040-02-08 Wed	89	—	unknown	19:20–00:05 (good, 4.75 h)	42.9° 20:45	10.53	18%	149.1°
2040-02-09 Thu	89	—	unknown	19:25–00:00 (good, 4.58 h)	42.9° 20:40	10.49	10%	142.6°
2040-02-10 Fri	89	—	unknown	19:25–23:55 (good, 4.5 h)	42.9° 20:35	10.45	4%	132.7°
2040-02-11 Sat	89	—	unknown	19:25–23:50 (good, 4.42 h)	42.9° 20:35	10.42	1%	121.1°
2040-02-12 Sun	89	—	unknown	19:25–23:50 (good, 4.42 h)	42.9° 20:30	10.38	0%	108.7°
2040-02-13 Mon	89	—	unknown	19:25–23:45 (good, 4.33 h)	42.9° 20:25	10.34	3%	96.3°
2040-02-14 Tue	89	—	unknown	19:30–23:40 (good, 4.17 h)	42.9° 20:20	10.3	7%	84.1°
2040-02-15 Wed	86	—	unknown	19:30–23:35 (good, 4.08 h)	42.9° 20:15	10.26	14%	72.3°
2040-02-16 Thu	77	—	unknown	19:30–23:30 (good, 4.0 h)	42.9° 20:15	10.22	22%	61.2°
2040-02-17 Fri	63	—	unknown	19:30–23:15 (good, 3.75 h)	42.9° 20:10	10.18	31%	51.0°
2040-02-18 Sat	49	—	unknown	19:35–23:00 (good, 3.42 h)	42.9° 20:05	10.14	41%	42.0°
2040-02-19 Sun	36	—	unknown	19:35–23:50 (marginal, 4.25 h)	42.9° 20:00	10.1	50%	34.8°
2040-02-20 Mon	25	—	unknown	19:35–23:35 (marginal, 4.0 h)	42.9° 19:55	10.06	60%	30.5°
2040-02-21 Tue	18	—	unknown	19:35–23:20 (marginal, 3.75 h)	42.9° 19:55	10.02	69%	30.1°
2040-02-22 Wed	14	—	unknown	19:35–23:00 (marginal, 3.42 h)	42.9° 19:50	9.97	77%	33.8°
2040-02-23 Thu	13	—	unknown	19:40–22:45 (marginal, 3.08 h)	42.9° 19:45	9.93	84%	40.3°
2040-02-24 Fri	14	—	unknown	19:40–22:40 (marginal, 3.0 h)	42.9° 19:40	9.89	91%	48.7°
2040-02-25 Sat	18	—	unknown	19:40–22:45 (marginal, 3.08 h)	42.9° 19:35	9.84	96%	58.2°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2040-01-27&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.