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: 10-17 (89), 10-18 (89), 10-19 (89), 10-20 (89), 10-21 (89) — by astronomy; check the weather when the night is within four days.

2031-09-28astronomy score per night — click a bar for that night2031-10-27

night of	astronomy	weather	overall	best window	highest	dark h	Moon	Moon sep.
2031-09-28 Sun	51	—	unknown	03:35–05:45 (good, 2.17 h)	42.9° 06:25	9.02	95%	102.9°
2031-09-29 Mon	35	—	unknown	04:05–05:45 (good, 1.67 h)	42.9° 06:25	9.07	99%	90.1°
2031-09-30 Tue	26	—	unknown	02:50–06:20 (marginal, 3.5 h)	42.9° 06:20	9.12	100%	77.4°
2031-10-01 Wed	20	—	unknown	03:00–05:50 (marginal, 2.83 h)	42.9° 06:15	9.17	98%	65.2°
2031-10-02 Thu	15	—	unknown	03:10–05:50 (marginal, 2.67 h)	42.9° 06:10	9.22	95%	53.6°
2031-10-03 Fri	12	—	unknown	03:20–05:50 (marginal, 2.5 h)	42.9° 06:05	9.27	89%	43.0°
2031-10-04 Sat	11	—	unknown	03:10–05:50 (marginal, 2.67 h)	42.9° 06:05	9.31	82%	33.9°
2031-10-05 Sun	14	—	unknown	02:50–05:55 (marginal, 3.08 h)	42.9° 06:00	9.36	73%	27.7°
2031-10-06 Mon	19	—	unknown	02:30–05:55 (marginal, 3.42 h)	42.9° 05:55	9.41	64%	25.8°
2031-10-07 Tue	27	—	unknown	02:10–05:55 (marginal, 3.75 h)	42.9° 05:50	9.45	55%	28.9°
2031-10-08 Wed	37	—	unknown	03:05–05:55 (good, 2.83 h)	42.9° 05:50	9.5	46%	35.6°
2031-10-09 Thu	49	—	unknown	02:50–05:55 (good, 3.08 h)	42.9° 05:45	9.54	36%	44.2°
2031-10-10 Fri	61	—	unknown	02:25–06:00 (good, 3.58 h)	42.9° 05:40	9.59	27%	53.9°
2031-10-11 Sat	71	—	unknown	02:20–06:00 (good, 3.67 h)	42.9° 05:35	9.64	19%	64.3°
2031-10-12 Sun	79	—	unknown	02:20–06:00 (good, 3.67 h)	42.9° 05:30	9.68	12%	75.1°
2031-10-13 Mon	82	—	unknown	02:15–06:00 (good, 3.75 h)	42.9° 05:30	9.72	6%	86.4°
2031-10-14 Tue	85	—	unknown	02:10–06:05 (good, 3.92 h)	42.9° 05:25	9.77	2%	97.9°
2031-10-15 Wed	86	—	unknown	02:05–06:05 (good, 4.0 h)	42.9° 05:20	9.81	0%	109.6°
2031-10-16 Thu	88	—	unknown	02:00–06:05 (good, 4.08 h)	42.9° 05:15	9.86	0%	121.3°
2031-10-17 Fri	89	—	unknown	02:00–06:05 (good, 4.08 h)	42.9° 05:10	9.9	3%	132.7°
2031-10-18 Sat	89	—	unknown	01:55–06:05 (good, 4.17 h)	42.9° 05:10	9.94	8%	143.2°
2031-10-19 Sun	89	—	unknown	01:50–06:10 (good, 4.33 h)	42.9° 05:05	9.98	15%	151.3°
2031-10-20 Mon	89	—	unknown	01:45–06:10 (good, 4.42 h)	42.9° 05:00	10.02	24%	154.3°
2031-10-21 Tue	89	—	unknown	01:40–06:10 (good, 4.5 h)	42.9° 04:55	10.07	34%	150.6°
2031-10-22 Wed	89	—	unknown	01:40–06:10 (good, 4.5 h)	42.9° 04:55	10.11	46%	142.1°
2031-10-23 Thu	89	—	unknown	01:35–06:15 (good, 4.67 h)	42.9° 04:50	10.15	57%	131.1°
2031-10-24 Fri	89	—	unknown	01:35–06:15 (good, 4.67 h)	42.9° 04:45	10.19	68%	119.2°
2031-10-25 Sat	89	—	unknown	01:40–05:15 (good, 4.58 h)	42.9° 03:40	10.23	78%	106.8°
2031-10-26 Sun	89	—	unknown	00:50–05:15 (good, 4.42 h)	42.9° 03:35	10.27	87%	94.3°
2031-10-27 Mon	80	—	unknown	01:55–05:15 (good, 3.33 h)	42.9° 03:35	10.31	93%	81.8°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2031-09-28&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.