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: 10-10 (77), 10-09 (76), 10-11 (75), 10-08 (74), 10-07 (73) — by astronomy; check the weather when the night is within four days.

2027-09-18astronomy score per night — click a bar for that night2027-10-17

night of	astronomy	weather	overall	best window	highest	dark h	Moon	Moon sep.
2027-09-18 Sat	11	—	unknown	03:50–05:35 (marginal, 1.75 h)	42.9° 07:05	8.52	91%	61.0°
2027-09-19 Sun	10	—	unknown	03:55–05:35 (marginal, 1.67 h)	42.9° 07:00	8.57	84%	51.2°
2027-09-20 Mon	10	—	unknown	03:50–05:35 (marginal, 1.75 h)	42.9° 07:00	8.62	76%	42.3°
2027-09-21 Tue	12	—	unknown	03:35–05:35 (marginal, 2.0 h)	42.9° 06:55	8.67	66%	35.6°
2027-09-22 Wed	17	—	unknown	03:15–05:40 (marginal, 2.42 h)	42.9° 06:50	8.72	56%	32.4°
2027-09-23 Thu	24	—	unknown	03:00–05:40 (marginal, 2.67 h)	42.9° 06:45	8.77	44%	34.3°
2027-09-24 Fri	33	—	unknown	03:50–05:40 (good, 1.83 h)	42.9° 06:45	8.82	33%	40.6°
2027-09-25 Sat	41	—	unknown	03:35–05:40 (good, 2.08 h)	42.9° 06:40	8.87	23%	50.0°
2027-09-26 Sun	50	—	unknown	03:20–05:45 (good, 2.42 h)	42.9° 06:35	8.92	14%	61.0°
2027-09-27 Mon	55	—	unknown	03:15–05:45 (good, 2.5 h)	42.9° 06:30	8.97	7%	73.0°
2027-09-28 Tue	58	—	unknown	03:15–05:45 (good, 2.5 h)	42.9° 06:25	9.02	2%	85.3°
2027-09-29 Wed	59	—	unknown	03:10–05:45 (good, 2.58 h)	42.9° 06:25	9.07	0%	97.7°
2027-09-30 Thu	61	—	unknown	03:05–05:45 (good, 2.67 h)	42.9° 06:20	9.12	1%	109.7°
2027-10-01 Fri	63	—	unknown	03:00–05:50 (good, 2.83 h)	42.9° 06:15	9.17	4%	121.0°
2027-10-02 Sat	65	—	unknown	02:55–05:50 (good, 2.92 h)	42.9° 06:10	9.22	10%	131.2°
2027-10-03 Sun	67	—	unknown	02:55–05:50 (good, 2.92 h)	42.9° 06:05	9.26	17%	139.7°
2027-10-04 Mon	68	—	unknown	02:50–05:50 (good, 3.0 h)	42.9° 06:05	9.31	26%	145.6°
2027-10-05 Tue	70	—	unknown	02:45–05:55 (good, 3.17 h)	42.9° 06:00	9.36	35%	147.7°
2027-10-06 Wed	72	—	unknown	02:40–05:55 (good, 3.25 h)	42.9° 05:55	9.4	44%	145.8°
2027-10-07 Thu	73	—	unknown	02:35–05:55 (good, 3.33 h)	42.9° 05:50	9.45	54%	140.6°
2027-10-08 Fri	74	—	unknown	02:35–05:55 (good, 3.33 h)	42.9° 05:50	9.5	63%	133.3°
2027-10-09 Sat	76	—	unknown	02:30–05:55 (good, 3.42 h)	42.9° 05:45	9.54	72%	124.7°
2027-10-10 Sun	77	—	unknown	02:35–06:00 (good, 3.42 h)	42.9° 05:40	9.59	80%	115.4°
2027-10-11 Mon	75	—	unknown	02:40–06:00 (good, 3.33 h)	42.9° 05:35	9.63	87%	105.5°
2027-10-12 Tue	70	—	unknown	02:45–06:00 (good, 3.25 h)	42.9° 05:30	9.68	93%	95.3°
2027-10-13 Wed	48	—	unknown	03:40–06:00 (good, 2.33 h)	42.9° 05:30	9.72	97%	84.9°
2027-10-14 Thu	37	—	unknown	05:25–06:05 (good, 0.67 h)	42.9° 05:25	9.77	99%	74.3°
2027-10-15 Fri	28	—	unknown	02:10–06:05 (marginal, 3.92 h)	42.9° 05:20	9.81	100%	63.8°
2027-10-16 Sat	20	—	unknown	02:25–06:05 (marginal, 3.67 h)	42.9° 05:15	9.85	98%	53.6°
2027-10-17 Sun	15	—	unknown	03:05–06:05 (marginal, 3.0 h)	42.9° 05:10	9.9	94%	44.3°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2027-09-18&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.