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: 03-11 (43), 03-12 (36), 03-13 (30), 03-23 (25), 03-24 (25) — by astronomy; check the weather when the night is within four days.

2027-03-11astronomy score per night — click a bar for that night2027-04-09

night of	astronomy	weather	overall	best window	highest	dark h	Moon	Moon sep.
2027-03-11 Thu	43	—	unknown	20:00–22:00 (good, 2.0 h)	42.9° 18:40	9.19	13%	58.3°
2027-03-12 Fri	36	—	unknown	20:00–21:45 (good, 1.75 h)	42.9° 18:35	9.14	21%	48.5°
2027-03-13 Sat	30	—	unknown	20:00–21:35 (good, 1.58 h)	42.9° 18:35	9.09	31%	40.1°
2027-03-14 Sun	22	—	unknown	20:00–20:30 (good, 0.5 h)	42.9° 18:30	9.04	42%	34.4°
2027-03-15 Mon	15	—	unknown	20:00–22:05 (marginal, 2.08 h)	42.9° 18:25	8.99	53%	33.2°
2027-03-16 Tue	11	—	unknown	20:05–21:50 (marginal, 1.75 h)	42.9° 18:20	8.94	64%	37.0°
2027-03-17 Wed	9	—	unknown	20:05–21:35 (marginal, 1.5 h)	42.9° 18:20	8.89	75%	44.7°
2027-03-18 Thu	9	—	unknown	20:05–21:30 (marginal, 1.42 h)	42.9° 18:15	8.84	84%	54.7°
2027-03-19 Fri	11	—	unknown	20:05–21:35 (marginal, 1.5 h)	42.9° 18:10	8.79	92%	66.0°
2027-03-20 Sat	13	—	unknown	20:10–21:40 (marginal, 1.5 h)	42.9° 18:05	8.73	97%	77.8°
2027-03-21 Sun	16	—	unknown	20:10–20:25 (good, 0.25 h)	42.9° 18:00	8.68	100%	89.8°
2027-03-22 Mon	20	—	unknown	20:10–20:55 (good, 0.75 h)	42.9° 18:00	8.63	100%	101.6°
2027-03-23 Tue	25	—	unknown	20:10–21:00 (good, 0.83 h)	42.9° 17:55	8.58	97%	112.9°
2027-03-24 Wed	25	—	unknown	20:15–21:10 (good, 0.92 h)	42.9° 17:50	8.53	92%	123.4°
2027-03-25 Thu	24	—	unknown	20:15–21:05 (good, 0.83 h)	42.9° 17:45	8.47	86%	132.8°
2027-03-26 Fri	22	—	unknown	20:15–21:00 (good, 0.75 h)	42.9° 17:40	8.42	78%	140.4°
2027-03-27 Sat	21	—	unknown	20:20–20:55 (good, 0.58 h)	42.9° 17:40	8.37	70%	145.5°
2027-03-28 Sun	19	—	unknown	21:20–21:55 (good, 0.58 h)	42.9° 18:35	8.31	60%	147.1°
2027-03-29 Mon	17	—	unknown	21:20–21:50 (good, 0.5 h)	42.9° 18:30	8.26	51%	144.9°
2027-03-30 Tue	15	—	unknown	21:20–21:45 (good, 0.42 h)	42.9° 18:25	8.2	42%	139.6°
2027-03-31 Wed	13	—	unknown	21:25–21:40 (good, 0.25 h)	42.9° 18:25	8.15	32%	132.3°
2027-04-01 Thu	12	—	unknown	21:25–21:40 (good, 0.25 h)	42.9° 18:20	8.1	24%	123.7°
2027-04-02 Fri	10	—	unknown	21:25–21:35 (good, 0.17 h)	42.9° 18:15	8.04	16%	114.2°
2027-04-03 Sat	9	—	unknown	21:25–21:30 (good, 0.08 h)	42.9° 18:10	7.99	10%	104.2°
2027-04-04 Sun	7	—	unknown	21:30–21:55 (marginal, 0.42 h)	42.9° 18:05	7.93	5%	93.7°
2027-04-05 Mon	6	—	unknown	21:30–21:55 (marginal, 0.42 h)	42.9° 18:05	7.87	1%	83.0°
2027-04-06 Tue	5	—	unknown	21:30–21:50 (marginal, 0.33 h)	42.9° 18:00	7.82	0%	72.1°
2027-04-07 Wed	4	—	unknown	21:30–21:45 (marginal, 0.25 h)	42.9° 17:55	7.76	1%	61.3°
2027-04-08 Thu	3	—	unknown	21:00–21:10 (marginal, 0.17 h)	42.9° 17:50	7.71	5%	51.0°
2027-04-09 Fri	2	—	unknown	—	42.9° 17:45	7.65	10%	41.9°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2027-03-11&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.