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: 10-02 (65), 10-01 (63), 09-30 (61), 09-29 (59), 09-28 (58) — by astronomy; check the weather when the night is within four days.

2027-09-03astronomy score per night — click a bar for that night2027-10-02

night of	astronomy	weather	overall	best window	highest	dark h	Moon	Moon sep.
2027-09-03 Fri	15	—	unknown	04:50–05:15 (good, 0.42 h)	42.9° 08:05	7.71	14%	114.6°
2027-09-04 Sat	17	—	unknown	04:45–05:15 (good, 0.5 h)	42.9° 08:00	7.76	22%	125.3°
2027-09-05 Sun	18	—	unknown	04:45–05:15 (good, 0.5 h)	42.9° 07:55	7.82	32%	134.7°
2027-09-06 Mon	21	—	unknown	04:40–05:20 (good, 0.67 h)	42.9° 07:55	7.87	42%	142.1°
2027-09-07 Tue	22	—	unknown	04:35–05:20 (good, 0.75 h)	42.9° 07:50	7.93	52%	146.6°
2027-09-08 Wed	24	—	unknown	04:30–05:20 (good, 0.83 h)	42.9° 07:45	7.98	61%	147.3°
2027-09-09 Thu	25	—	unknown	04:30–05:20 (good, 0.83 h)	42.9° 07:40	8.04	70%	144.3°
2027-09-10 Fri	27	—	unknown	04:25–05:25 (good, 1.0 h)	42.9° 07:40	8.09	79%	138.3°
2027-09-11 Sat	29	—	unknown	04:20–05:25 (good, 1.08 h)	42.9° 07:35	8.15	86%	130.6°
2027-09-12 Sun	30	—	unknown	04:15–05:25 (good, 1.17 h)	42.9° 07:30	8.2	92%	121.8°
2027-09-13 Mon	29	—	unknown	04:25–05:25 (good, 1.0 h)	42.9° 07:25	8.25	96%	112.3°
2027-09-14 Tue	23	—	unknown	04:30–05:30 (good, 1.0 h)	42.9° 07:20	8.31	99%	102.3°
2027-09-15 Wed	20	—	unknown	04:50–05:30 (good, 0.67 h)	42.9° 07:20	8.36	100%	92.1°
2027-09-16 Thu	16	—	unknown	03:40–05:30 (marginal, 1.83 h)	42.9° 07:15	8.41	99%	81.7°
2027-09-17 Fri	13	—	unknown	03:45–05:30 (marginal, 1.75 h)	42.9° 07:10	8.46	96%	71.3°
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°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2027-09-03&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.