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.

2040-04-16astronomy score per night — click a bar for that night2040-05-15

night of	weather	overall	best window	highest	dark h	Moon	Moon sep.
2040-04-16 Mon	—	unknown	—	42.9° 17:15	7.2	26%	31.4°
2040-04-17 Tue	—	unknown	—	42.9° 17:15	7.14	35%	36.0°
2040-04-18 Wed	—	unknown	—	42.9° 17:10	7.08	44%	43.2°
2040-04-19 Thu	—	unknown	—	42.9° 17:05	7.03	54%	51.8°
2040-04-20 Fri	—	unknown	—	42.9° 17:00	6.97	63%	61.4°
2040-04-21 Sat	—	unknown	—	42.9° 16:55	6.91	72%	71.6°
2040-04-22 Sun	—	unknown	—	42.9° 16:55	6.85	81%	82.3°
2040-04-23 Mon	—	unknown	—	42.9° 16:50	6.79	88%	93.4°
2040-04-24 Tue	—	unknown	—	42.9° 16:45	6.74	94%	104.7°
2040-04-25 Wed	—	unknown	—	42.9° 16:40	6.68	98%	116.2°
2040-04-26 Thu	—	unknown	—	42.9° 16:40	6.62	100%	127.4°
2040-04-27 Fri	—	unknown	—	42.9° 16:35	6.56	99%	137.7°
2040-04-28 Sat	—	unknown	—	42.9° 16:30	6.5	96%	145.8°
2040-04-29 Sun	—	unknown	—	42.9° 16:25	6.44	90%	149.7°
2040-04-30 Mon	—	unknown	—	42.9° 16:20	6.39	81%	147.5°
2040-05-01 Tue	—	unknown	—	42.9° 16:20	6.33	71%	140.4°
2040-05-02 Wed	—	unknown	—	42.9° 16:15	6.27	60%	130.6°
2040-05-03 Thu	—	unknown	—	42.9° 16:10	6.21	49%	119.5°
2040-05-04 Fri	—	unknown	—	42.9° 16:05	6.16	38%	107.9°
2040-05-05 Sat	—	unknown	—	42.9° 16:00	6.1	27%	96.2°
2040-05-06 Sun	—	unknown	—	42.9° 16:00	6.04	18%	84.6°
2040-05-07 Mon	—	unknown	—	42.9° 15:55	5.98	11%	73.2°
2040-05-08 Tue	—	unknown	—	42.9° 15:50	5.93	5%	62.2°
2040-05-09 Wed	—	unknown	—	42.9° 15:45	5.87	2%	52.0°
2040-05-10 Thu	—	unknown	—	42.9° 15:45	5.82	0%	42.8°
2040-05-11 Fri	—	unknown	—	42.9° 15:40	5.76	1%	35.5°
2040-05-12 Sat	—	unknown	—	42.9° 15:35	5.71	3%	31.0°
2040-05-13 Sun	—	unknown	—	42.9° 15:30	5.65	7%	30.7°
2040-05-14 Mon	—	unknown	—	42.9° 15:25	5.6	13%	34.3°
2040-05-15 Tue	—	unknown	—	42.9° 15:25	5.55	20%	40.8°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2040-04-16&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.