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: 08-19 (1), 08-20 (1) — by astronomy; check the weather when the night is within four days.

2040-07-22astronomy score per night — click a bar for that night2040-08-20

night of	astronomy	weather	overall	best window	highest	dark h	Moon	Moon sep.
2040-07-22 Sun	0	—	unknown	—	42.9° 10:50	5.35	98%	142.0°
2040-07-23 Mon	0	—	unknown	—	42.9° 10:50	5.4	100%	131.9°
2040-07-24 Tue	0	—	unknown	—	42.9° 10:45	5.45	99%	120.0°
2040-07-25 Wed	0	—	unknown	—	42.9° 10:40	5.5	95%	107.5°
2040-07-26 Thu	0	—	unknown	—	42.9° 10:35	5.56	88%	94.9°
2040-07-27 Fri	0	—	unknown	—	42.9° 10:30	5.61	80%	82.6°
2040-07-28 Sat	0	—	unknown	—	42.9° 10:30	5.66	70%	70.8°
2040-07-29 Sun	0	—	unknown	—	42.9° 10:25	5.72	60%	59.8°
2040-07-30 Mon	0	—	unknown	—	42.9° 10:20	5.77	49%	49.7°
2040-07-31 Tue	0	—	unknown	—	42.9° 10:15	5.83	39%	40.9°
2040-08-01 Wed	0	—	unknown	—	42.9° 10:10	5.88	30%	34.2°
2040-08-02 Thu	0	—	unknown	—	42.9° 10:10	5.94	22%	30.7°
2040-08-03 Fri	0	—	unknown	—	42.9° 10:05	5.99	14%	31.2°
2040-08-04 Sat	0	—	unknown	—	42.9° 10:00	6.05	8%	35.5°
2040-08-05 Sun	0	—	unknown	—	42.9° 09:55	6.1	4%	42.4°
2040-08-06 Mon	0	—	unknown	—	42.9° 09:55	6.16	1%	50.9°
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°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2040-07-22&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.