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: 09-30 (63), 09-29 (60), 09-28 (59), 09-27 (57), 09-26 (55) — by astronomy; check the weather when the night is within four days.

2041-09-01astronomy score per night — click a bar for that night2041-09-30

night of	astronomy	weather	overall	best window	highest	dark h	Moon	Moon sep.
2041-09-01 Sun	13	—	unknown	04:55–05:15 (good, 0.33 h)	42.9° 08:10	7.63	32%	135.8°
2041-09-02 Mon	15	—	unknown	04:55–05:15 (good, 0.33 h)	42.9° 08:10	7.69	42%	142.9°
2041-09-03 Tue	16	—	unknown	04:50–05:15 (good, 0.42 h)	42.9° 08:05	7.74	52%	147.2°
2041-09-04 Wed	17	—	unknown	04:45–05:15 (good, 0.5 h)	42.9° 08:00	7.8	63%	147.1°
2041-09-05 Thu	21	—	unknown	04:40–05:20 (good, 0.67 h)	42.9° 07:55	7.85	73%	142.2°
2041-09-06 Fri	22	—	unknown	04:40–05:20 (good, 0.67 h)	42.9° 07:50	7.91	83%	133.8°
2041-09-07 Sat	23	—	unknown	04:35–05:20 (good, 0.75 h)	42.9° 07:50	7.96	91%	123.1°
2041-09-08 Sun	22	—	unknown	04:45–05:20 (good, 0.58 h)	42.9° 07:45	8.02	96%	111.1°
2041-09-09 Mon	17	—	unknown	04:50–05:25 (good, 0.58 h)	42.9° 07:40	8.07	100%	98.4°
2041-09-10 Tue	14	—	unknown	03:55–05:25 (marginal, 1.5 h)	42.9° 07:35	8.13	100%	85.5°
2041-09-11 Wed	11	—	unknown	04:05–05:25 (marginal, 1.33 h)	42.9° 07:30	8.18	96%	72.9°
2041-09-12 Thu	9	—	unknown	04:10–05:25 (marginal, 1.25 h)	42.9° 07:30	8.23	91%	60.8°
2041-09-13 Fri	8	—	unknown	04:15–05:30 (marginal, 1.25 h)	42.9° 07:25	8.29	83%	49.9°
2041-09-14 Sat	8	—	unknown	04:05–05:30 (marginal, 1.42 h)	42.9° 07:20	8.34	74%	40.8°
2041-09-15 Sun	10	—	unknown	03:55–05:30 (marginal, 1.58 h)	42.9° 07:15	8.39	63%	34.5°
2041-09-16 Mon	14	—	unknown	03:35–05:30 (marginal, 1.92 h)	42.9° 07:10	8.44	53%	32.3°
2041-09-17 Tue	20	—	unknown	03:25–05:35 (marginal, 2.17 h)	42.9° 07:10	8.5	43%	34.5°
2041-09-18 Wed	26	—	unknown	04:15–05:35 (good, 1.33 h)	42.9° 07:05	8.55	33%	40.1°
2041-09-19 Thu	33	—	unknown	04:00–05:35 (good, 1.58 h)	42.9° 07:00	8.6	25%	47.7°
2041-09-20 Fri	39	—	unknown	03:50–05:35 (good, 1.75 h)	42.9° 06:55	8.65	17%	56.5°
2041-09-21 Sat	44	—	unknown	03:40–05:40 (good, 2.0 h)	42.9° 06:55	8.7	10%	65.8°
2041-09-22 Sun	47	—	unknown	03:35–05:40 (good, 2.08 h)	42.9° 06:50	8.75	5%	75.6°
2041-09-23 Mon	50	—	unknown	03:30–05:40 (good, 2.17 h)	42.9° 06:45	8.8	2%	85.5°
2041-09-24 Tue	52	—	unknown	03:25–05:40 (good, 2.25 h)	42.9° 06:40	8.85	0%	95.5°
2041-09-25 Wed	53	—	unknown	03:25–05:40 (good, 2.25 h)	42.9° 06:35	8.9	0%	105.5°
2041-09-26 Thu	55	—	unknown	03:20–05:45 (good, 2.42 h)	42.9° 06:35	8.95	2%	115.4°
2041-09-27 Fri	57	—	unknown	03:15–05:45 (good, 2.5 h)	42.9° 06:30	9.0	6%	124.9°
2041-09-28 Sat	59	—	unknown	03:10–05:45 (good, 2.58 h)	42.9° 06:25	9.05	12%	133.7°
2041-09-29 Sun	60	—	unknown	03:05–05:45 (good, 2.67 h)	42.9° 06:20	9.1	19%	141.3°
2041-09-30 Mon	63	—	unknown	03:05–05:50 (good, 2.75 h)	42.9° 06:15	9.15	27%	146.3°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2041-09-01&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.