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: 09-05 (21), 09-04 (17), 09-03 (16), 09-02 (13), 09-01 (11) — by astronomy; check the weather when the night is within four days.

2040-08-07astronomy score per night — click a bar for that night2040-09-05

night of	astronomy	weather	overall	best window	highest	dark h	Moon	Moon sep.
2040-08-07 Tue	0	—	unknown	—	42.9° 09:50	6.22	0%	60.2°
2040-08-08 Wed	0	—	unknown	—	42.9° 09:45	6.28	1%	70.1°
2040-08-09 Thu	0	—	unknown	—	42.9° 09:40	6.33	4%	80.4°
2040-08-10 Fri	0	—	unknown	—	42.9° 09:35	6.39	8%	90.9°
2040-08-11 Sat	0	—	unknown	—	42.9° 09:35	6.45	14%	101.5°
2040-08-12 Sun	0	—	unknown	—	42.9° 09:30	6.5	22%	112.2°
2040-08-13 Mon	0	—	unknown	—	42.9° 09:25	6.56	31%	122.7°
2040-08-14 Tue	0	—	unknown	—	42.9° 09:20	6.62	41%	132.7°
2040-08-15 Wed	0	—	unknown	—	42.9° 09:15	6.68	52%	141.5°
2040-08-16 Thu	0	—	unknown	—	42.9° 09:15	6.73	63%	147.8°
2040-08-17 Fri	0	—	unknown	—	42.9° 09:10	6.79	73%	149.3°
2040-08-18 Sat	0	—	unknown	—	42.9° 09:05	6.85	83%	145.0°
2040-08-19 Sun	1	—	unknown	—	42.9° 09:00	6.91	91%	136.4°
2040-08-20 Mon	1	—	unknown	—	42.9° 09:00	6.96	97%	125.4°
2040-08-21 Tue	1	—	unknown	—	42.9° 08:55	7.02	100%	113.2°
2040-08-22 Wed	1	—	unknown	—	42.9° 08:50	7.08	99%	100.5°
2040-08-23 Thu	1	—	unknown	—	42.9° 08:45	7.14	96%	87.9°
2040-08-24 Fri	1	—	unknown	—	42.9° 08:40	7.19	91%	75.6°
2040-08-25 Sat	1	—	unknown	—	42.9° 08:40	7.25	84%	63.9°
2040-08-26 Sun	1	—	unknown	—	42.9° 08:35	7.31	75%	53.2°
2040-08-27 Mon	2	—	unknown	—	42.9° 08:30	7.36	65%	43.7°
2040-08-28 Tue	2	—	unknown	04:55–05:05 (marginal, 0.17 h)	42.9° 08:25	7.42	55%	36.2°
2040-08-29 Wed	4	—	unknown	04:45–05:10 (marginal, 0.42 h)	42.9° 08:20	7.48	46%	31.6°
2040-08-30 Thu	5	—	unknown	04:35–05:10 (marginal, 0.58 h)	42.9° 08:20	7.53	36%	30.9°
2040-08-31 Fri	7	—	unknown	04:30–05:10 (marginal, 0.67 h)	42.9° 08:15	7.59	27%	34.2°
2040-09-01 Sat	11	—	unknown	05:05–05:15 (good, 0.17 h)	42.9° 08:10	7.65	19%	40.5°
2040-09-02 Sun	13	—	unknown	05:00–05:15 (good, 0.25 h)	42.9° 08:05	7.7	12%	48.5°
2040-09-03 Mon	16	—	unknown	04:50–05:15 (good, 0.42 h)	42.9° 08:05	7.76	7%	57.6°
2040-09-04 Tue	17	—	unknown	04:45–05:15 (good, 0.5 h)	42.9° 08:00	7.81	3%	67.4°
2040-09-05 Wed	21	—	unknown	04:40–05:20 (good, 0.67 h)	42.9° 07:55	7.87	1%	77.6°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2040-08-07&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.