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: 09-21 (47), 09-22 (47), 09-20 (45), 09-23 (45), 09-19 (43) — by astronomy; check the weather when the night is within four days.

2045-08-31astronomy score per night — click a bar for that night2045-09-29

night of	astronomy	weather	overall	best window	highest	dark h	Moon	Moon sep.
2045-08-31 Thu	3	—	unknown	04:50–05:10 (marginal, 0.33 h)	42.9° 08:15	7.58	83%	63.1°
2045-09-01 Fri	4	—	unknown	04:50–05:15 (marginal, 0.42 h)	42.9° 08:10	7.63	75%	53.5°
2045-09-02 Sat	5	—	unknown	04:45–05:15 (marginal, 0.5 h)	42.9° 08:10	7.69	66%	44.8°
2045-09-03 Sun	6	—	unknown	04:30–05:15 (marginal, 0.75 h)	42.9° 08:05	7.74	55%	37.7°
2045-09-04 Mon	8	—	unknown	04:20–05:15 (marginal, 0.92 h)	42.9° 08:00	7.8	44%	33.6°
2045-09-05 Tue	13	—	unknown	05:10–05:20 (good, 0.17 h)	42.9° 07:55	7.86	34%	34.1°
2045-09-06 Wed	17	—	unknown	04:50–05:20 (good, 0.5 h)	42.9° 07:50	7.91	23%	39.4°
2045-09-07 Thu	20	—	unknown	04:40–05:20 (good, 0.67 h)	42.9° 07:50	7.96	14%	48.1°
2045-09-08 Fri	23	—	unknown	04:30–05:20 (good, 0.83 h)	42.9° 07:45	8.02	7%	59.0°
2045-09-09 Sat	27	—	unknown	04:25–05:25 (good, 1.0 h)	42.9° 07:40	8.07	2%	71.0°
2045-09-10 Sun	28	—	unknown	04:20–05:25 (good, 1.08 h)	42.9° 07:35	8.13	0%	83.5°
2045-09-11 Mon	30	—	unknown	04:20–05:25 (good, 1.08 h)	42.9° 07:30	8.18	1%	96.0°
2045-09-12 Tue	31	—	unknown	04:15–05:25 (good, 1.17 h)	42.9° 07:30	8.23	5%	108.2°
2045-09-13 Wed	33	—	unknown	04:10–05:30 (good, 1.33 h)	42.9° 07:25	8.29	11%	119.7°
2045-09-14 Thu	35	—	unknown	04:05–05:30 (good, 1.42 h)	42.9° 07:20	8.34	20%	130.0°
2045-09-15 Fri	36	—	unknown	04:00–05:30 (good, 1.5 h)	42.9° 07:15	8.39	29%	138.6°
2045-09-16 Sat	38	—	unknown	04:00–05:30 (good, 1.5 h)	42.9° 07:15	8.45	39%	144.5°
2045-09-17 Sun	40	—	unknown	03:55–05:35 (good, 1.67 h)	42.9° 07:10	8.5	49%	146.9°
2045-09-18 Mon	42	—	unknown	03:50–05:35 (good, 1.75 h)	42.9° 07:05	8.55	58%	145.2°
2045-09-19 Tue	43	—	unknown	03:45–05:35 (good, 1.83 h)	42.9° 07:00	8.6	68%	140.2°
2045-09-20 Wed	45	—	unknown	03:45–05:35 (good, 1.83 h)	42.9° 06:55	8.65	76%	133.1°
2045-09-21 Thu	47	—	unknown	03:40–05:40 (good, 2.0 h)	42.9° 06:55	8.7	84%	124.6°
2045-09-22 Fri	47	—	unknown	03:45–05:40 (good, 1.92 h)	42.9° 06:50	8.75	90%	115.5°
2045-09-23 Sat	45	—	unknown	03:50–05:40 (good, 1.83 h)	42.9° 06:45	8.81	95%	105.9°
2045-09-24 Sun	34	—	unknown	03:55–05:40 (good, 1.75 h)	42.9° 06:40	8.86	98%	95.9°
2045-09-25 Mon	28	—	unknown	04:50–05:40 (good, 0.83 h)	42.9° 06:35	8.91	100%	85.8°
2045-09-26 Tue	22	—	unknown	03:05–05:45 (marginal, 2.67 h)	42.9° 06:35	8.96	100%	75.6°
2045-09-27 Wed	17	—	unknown	03:15–05:45 (marginal, 2.5 h)	42.9° 06:30	9.0	97%	65.5°
2045-09-28 Thu	14	—	unknown	03:20–05:45 (marginal, 2.42 h)	42.9° 06:25	9.05	93%	55.7°
2045-09-29 Fri	12	—	unknown	03:25–05:45 (marginal, 2.33 h)	42.9° 06:20	9.1	87%	46.6°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2045-08-31&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.