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: 03-13 (44), 03-14 (43), 03-15 (40), 03-16 (39), 03-17 (38) — by astronomy; check the weather when the night is within four days.

2039-03-13astronomy score per night — click a bar for that night2039-04-11

night of	astronomy	weather	overall	best window	highest	dark h	Moon	Moon sep.
2039-03-13 Sun	44	—	unknown	20:00–21:55 (good, 1.92 h)	42.9° 18:35	9.08	86%	129.7°
2039-03-14 Mon	43	—	unknown	20:00–21:50 (good, 1.83 h)	42.9° 18:30	9.03	77%	140.4°
2039-03-15 Tue	40	—	unknown	20:05–21:45 (good, 1.67 h)	42.9° 18:25	8.98	67%	148.5°
2039-03-16 Wed	39	—	unknown	20:05–21:40 (good, 1.58 h)	42.9° 18:20	8.93	56%	151.8°
2039-03-17 Thu	38	—	unknown	20:05–21:35 (good, 1.5 h)	42.9° 18:20	8.88	44%	148.9°
2039-03-18 Fri	36	—	unknown	20:05–21:35 (good, 1.5 h)	42.9° 18:15	8.83	33%	141.5°
2039-03-19 Sat	34	—	unknown	20:05–21:30 (good, 1.42 h)	42.9° 18:10	8.78	24%	131.7°
2039-03-20 Sun	32	—	unknown	20:10–21:25 (good, 1.25 h)	42.9° 18:05	8.73	15%	120.9°
2039-03-21 Mon	30	—	unknown	20:10–21:20 (good, 1.17 h)	42.9° 18:00	8.68	8%	109.7°
2039-03-22 Tue	29	—	unknown	20:10–21:15 (good, 1.08 h)	42.9° 18:00	8.63	4%	98.3°
2039-03-23 Wed	28	—	unknown	20:10–21:15 (good, 1.08 h)	42.9° 17:55	8.57	1%	87.0°
2039-03-24 Thu	25	—	unknown	20:15–21:10 (good, 0.92 h)	42.9° 17:50	8.52	0%	76.0°
2039-03-25 Fri	24	—	unknown	20:15–21:05 (good, 0.83 h)	42.9° 17:45	8.47	2%	65.3°
2039-03-26 Sat	22	—	unknown	20:15–21:00 (good, 0.75 h)	42.9° 17:40	8.42	5%	55.1°
2039-03-27 Sun	19	—	unknown	21:20–21:55 (good, 0.58 h)	42.9° 18:40	8.36	10%	45.7°
2039-03-28 Mon	16	—	unknown	21:20–21:45 (good, 0.42 h)	42.9° 18:35	8.31	16%	37.4°
2039-03-29 Tue	13	—	unknown	21:20–21:35 (good, 0.25 h)	42.9° 18:30	8.25	23%	31.2°
2039-03-30 Wed	10	—	unknown	20:45–22:15 (marginal, 1.5 h)	42.9° 18:25	8.2	32%	28.4°
2039-03-31 Thu	7	—	unknown	21:25–22:10 (marginal, 0.75 h)	42.9° 18:25	8.15	41%	30.0°
2039-04-01 Fri	5	—	unknown	21:25–22:00 (marginal, 0.58 h)	42.9° 18:20	8.09	50%	35.4°
2039-04-02 Sat	4	—	unknown	21:25–21:50 (marginal, 0.42 h)	42.9° 18:15	8.04	60%	43.4°
2039-04-03 Sun	3	—	unknown	21:25–21:40 (marginal, 0.25 h)	42.9° 18:10	7.98	70%	53.1°
2039-04-04 Mon	2	—	unknown	21:30–21:40 (marginal, 0.17 h)	42.9° 18:05	7.93	79%	63.8°
2039-04-05 Tue	2	—	unknown	21:30–21:40 (marginal, 0.17 h)	42.9° 18:05	7.87	87%	75.4°
2039-04-06 Wed	2	—	unknown	21:30–21:45 (marginal, 0.25 h)	42.9° 18:00	7.81	93%	87.5°
2039-04-07 Thu	2	—	unknown	21:35–21:45 (marginal, 0.17 h)	42.9° 17:55	7.76	98%	100.0°
2039-04-08 Fri	2	—	unknown	21:35–21:40 (marginal, 0.08 h)	42.9° 17:50	7.7	100%	112.7°
2039-04-09 Sat	2	—	unknown	21:35–21:40 (marginal, 0.08 h)	42.9° 17:45	7.64	99%	125.1°
2039-04-10 Sun	2	—	unknown	21:00–21:05 (marginal, 0.08 h)	42.9° 17:45	7.59	95%	136.7°
2039-04-11 Mon	1	—	unknown	—	42.9° 17:40	7.53	89%	146.1°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2039-03-13&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.