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: 02-09 (89), 02-10 (89), 02-11 (89), 02-12 (89), 02-13 (89) — by astronomy; check the weather when the night is within four days.

2040-02-09astronomy score per night — click a bar for that night2040-03-09

night of	astronomy	weather	overall	best window	highest	dark h	Moon	Moon sep.
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°
2040-02-26 Sun	24	—	unknown	19:40–22:55 (marginal, 3.25 h)	42.9° 19:35	9.8	99%	68.5°
2040-02-27 Mon	30	—	unknown	19:45–20:00 (good, 0.25 h)	42.9° 19:30	9.75	100%	79.2°
2040-02-28 Tue	39	—	unknown	19:45–21:35 (good, 1.83 h)	42.9° 19:25	9.71	99%	90.2°
2040-02-29 Wed	55	—	unknown	19:45–22:15 (good, 2.5 h)	42.9° 19:20	9.66	96%	101.4°
2040-03-01 Thu	61	—	unknown	19:45–22:25 (good, 2.67 h)	42.9° 19:20	9.62	91%	112.7°
2040-03-02 Fri	61	—	unknown	19:50–22:25 (good, 2.58 h)	42.9° 19:15	9.57	84%	123.7°
2040-03-03 Sat	60	—	unknown	19:50–22:30 (good, 2.67 h)	42.9° 19:10	9.53	75%	134.0°
2040-03-04 Sun	58	—	unknown	19:50–22:25 (good, 2.58 h)	42.9° 19:05	9.48	65%	143.0°
2040-03-05 Mon	57	—	unknown	19:50–22:20 (good, 2.5 h)	42.9° 19:00	9.43	54%	148.9°
2040-03-06 Tue	55	—	unknown	19:55–22:15 (good, 2.33 h)	42.9° 19:00	9.39	43%	149.7°
2040-03-07 Wed	53	—	unknown	19:55–22:15 (good, 2.33 h)	42.9° 18:55	9.34	32%	144.9°
2040-03-08 Thu	51	—	unknown	19:55–22:10 (good, 2.25 h)	42.9° 18:50	9.29	22%	136.2°
2040-03-09 Fri	50	—	unknown	19:55–22:05 (good, 2.17 h)	42.9° 18:45	9.24	13%	125.4°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2040-02-09&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.