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: 09-20 (44), 09-19 (43), 09-21 (43), 09-18 (42), 09-17 (40) — by astronomy; check the weather when the night is within four days.

2037-08-26astronomy score per night — click a bar for that night2037-09-24

night of	astronomy	weather	overall	best window	highest	dark h	Moon	Moon sep.
2037-08-26 Wed	2	—	unknown	04:50–05:05 (marginal, 0.25 h)	42.9° 08:35	7.29	99%	93.9°
2037-08-27 Thu	2	—	unknown	04:55–05:05 (marginal, 0.17 h)	42.9° 08:30	7.35	96%	83.2°
2037-08-28 Fri	3	—	unknown	04:55–05:05 (marginal, 0.17 h)	42.9° 08:25	7.41	91%	72.6°
2037-08-29 Sat	3	—	unknown	05:00–05:10 (marginal, 0.17 h)	42.9° 08:25	7.46	85%	62.2°
2037-08-30 Sun	3	—	unknown	05:00–05:10 (marginal, 0.17 h)	42.9° 08:20	7.52	78%	52.0°
2037-08-31 Mon	3	—	unknown	04:55–05:10 (marginal, 0.25 h)	42.9° 08:15	7.57	69%	42.3°
2037-09-01 Tue	4	—	unknown	04:45–05:10 (marginal, 0.42 h)	42.9° 08:10	7.63	60%	33.6°
2037-09-02 Wed	6	—	unknown	04:30–05:15 (marginal, 0.75 h)	42.9° 08:05	7.69	50%	27.4°
2037-09-03 Thu	8	—	unknown	04:20–05:15 (marginal, 0.92 h)	42.9° 08:05	7.74	40%	25.8°
2037-09-04 Fri	11	—	unknown	05:10–05:15 (good, 0.08 h)	42.9° 08:00	7.8	29%	30.0°
2037-09-05 Sat	16	—	unknown	04:50–05:20 (good, 0.5 h)	42.9° 07:55	7.85	20%	38.6°
2037-09-06 Sun	20	—	unknown	04:40–05:20 (good, 0.67 h)	42.9° 07:50	7.91	12%	49.7°
2037-09-07 Mon	22	—	unknown	04:35–05:20 (good, 0.75 h)	42.9° 07:50	7.96	5%	62.2°
2037-09-08 Tue	24	—	unknown	04:30–05:20 (good, 0.83 h)	42.9° 07:45	8.02	1%	75.5°
2037-09-09 Wed	26	—	unknown	04:25–05:25 (good, 1.0 h)	42.9° 07:40	8.07	0%	89.2°
2037-09-10 Thu	28	—	unknown	04:20–05:25 (good, 1.08 h)	42.9° 07:35	8.12	2%	102.9°
2037-09-11 Fri	30	—	unknown	04:20–05:25 (good, 1.08 h)	42.9° 07:30	8.18	7%	116.3°
2037-09-12 Sat	31	—	unknown	04:15–05:25 (good, 1.17 h)	42.9° 07:30	8.23	15%	129.0°
2037-09-13 Sun	33	—	unknown	04:10–05:30 (good, 1.33 h)	42.9° 07:25	8.28	24%	140.3°
2037-09-14 Mon	35	—	unknown	04:05–05:30 (good, 1.42 h)	42.9° 07:20	8.34	34%	149.3°
2037-09-15 Tue	36	—	unknown	04:00–05:30 (good, 1.5 h)	42.9° 07:15	8.39	45%	154.0°
2037-09-16 Wed	38	—	unknown	04:00–05:30 (good, 1.5 h)	42.9° 07:10	8.44	55%	152.8°
2037-09-17 Thu	40	—	unknown	03:55–05:35 (good, 1.67 h)	42.9° 07:10	8.49	65%	146.6°
2037-09-18 Fri	42	—	unknown	03:50–05:35 (good, 1.75 h)	42.9° 07:05	8.55	74%	137.9°
2037-09-19 Sat	43	—	unknown	03:45–05:35 (good, 1.83 h)	42.9° 07:00	8.6	82%	128.1°
2037-09-20 Sun	44	—	unknown	03:50–05:35 (good, 1.75 h)	42.9° 06:55	8.65	89%	117.8°
2037-09-21 Mon	43	—	unknown	03:55–05:40 (good, 1.75 h)	42.9° 06:55	8.7	94%	107.3°
2037-09-22 Tue	33	—	unknown	04:00–05:40 (good, 1.67 h)	42.9° 06:50	8.75	98%	96.7°
2037-09-23 Wed	28	—	unknown	04:35–05:40 (good, 1.08 h)	42.9° 06:45	8.8	100%	86.0°
2037-09-24 Thu	22	—	unknown	03:10–05:40 (marginal, 2.5 h)	42.9° 06:40	8.85	100%	75.4°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2037-08-26&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.