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: 09-02 (14), 09-01 (11), 08-31 (9), 08-30 (7), 08-29 (6) — by astronomy; check the weather when the night is within four days.

2043-08-04astronomy score per night — click a bar for that night2043-09-02

night of	astronomy	weather	overall	best window	highest	dark h	Moon	Moon sep.
2043-08-04 Tue	0	—	unknown	—	42.9° 10:05	6.01	0%	55.9°
2043-08-05 Wed	0	—	unknown	—	42.9° 10:00	6.06	1%	66.6°
2043-08-06 Thu	0	—	unknown	—	42.9° 09:55	6.12	4%	77.5°
2043-08-07 Fri	0	—	unknown	—	42.9° 09:50	6.18	9%	88.3°
2043-08-08 Sat	0	—	unknown	—	42.9° 09:50	6.23	16%	98.9°
2043-08-09 Sun	0	—	unknown	—	42.9° 09:45	6.29	24%	109.1°
2043-08-10 Mon	0	—	unknown	—	42.9° 09:40	6.35	33%	118.7°
2043-08-11 Tue	0	—	unknown	—	42.9° 09:35	6.41	42%	127.7°
2043-08-12 Wed	0	—	unknown	—	42.9° 09:30	6.46	51%	135.6°
2043-08-13 Thu	0	—	unknown	—	42.9° 09:30	6.52	61%	141.8°
2043-08-14 Fri	0	—	unknown	—	42.9° 09:25	6.58	70%	145.6°
2043-08-15 Sat	0	—	unknown	—	42.9° 09:20	6.64	78%	145.9°
2043-08-16 Sun	0	—	unknown	—	42.9° 09:15	6.69	86%	142.5°
2043-08-17 Mon	0	—	unknown	—	42.9° 09:10	6.75	92%	136.2°
2043-08-18 Tue	0	—	unknown	—	42.9° 09:10	6.81	97%	127.8°
2043-08-19 Wed	0	—	unknown	—	42.9° 09:05	6.87	99%	118.0°
2043-08-20 Thu	1	—	unknown	—	42.9° 09:00	6.92	100%	107.4°
2043-08-21 Fri	1	—	unknown	—	42.9° 08:55	6.98	98%	96.2°
2043-08-22 Sat	1	—	unknown	—	42.9° 08:55	7.04	94%	84.7°
2043-08-23 Sun	1	—	unknown	—	42.9° 08:50	7.1	87%	73.2°
2043-08-24 Mon	1	—	unknown	—	42.9° 08:45	7.15	78%	61.9°
2043-08-25 Tue	1	—	unknown	—	42.9° 08:40	7.21	68%	51.4°
2043-08-26 Wed	2	—	unknown	—	42.9° 08:35	7.27	57%	42.3°
2043-08-27 Thu	2	—	unknown	04:55–05:05 (marginal, 0.17 h)	42.9° 08:35	7.32	46%	36.0°
2043-08-28 Fri	3	—	unknown	04:45–05:05 (marginal, 0.33 h)	42.9° 08:30	7.38	34%	33.9°
2043-08-29 Sat	6	—	unknown	04:40–05:10 (marginal, 0.5 h)	42.9° 08:25	7.44	24%	36.8°
2043-08-30 Sun	7	—	unknown	04:35–05:10 (marginal, 0.58 h)	42.9° 08:20	7.49	15%	43.6°
2043-08-31 Mon	9	—	unknown	05:05–05:10 (good, 0.08 h)	42.9° 08:15	7.55	8%	52.6°
2043-09-01 Tue	11	—	unknown	05:00–05:10 (good, 0.17 h)	42.9° 08:15	7.6	3%	62.8°
2043-09-02 Wed	14	—	unknown	04:55–05:15 (good, 0.33 h)	42.9° 08:10	7.66	0%	73.6°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2043-08-04&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.