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 HD 189733: 05-23 (100), 05-24 (100), 05-25 (100), 05-26 (100), 05-27 (100) — by astronomy; check the weather when the night is within four days.

2031-05-18astronomy score per night — click a bar for that night2031-06-16

night of	astronomy	weather	overall	best window	highest	dark h	Moon	Moon sep.
2031-05-18 Sun	94	—	unknown	00:35–04:05 (good, 3.5 h)	71.1° 05:35	5.43	6%	82.4°
2031-05-19 Mon	94	—	unknown	00:30–04:00 (good, 3.5 h)	71.1° 05:35	5.38	2%	92.4°
2031-05-20 Tue	96	—	unknown	00:30–04:00 (good, 3.5 h)	71.1° 05:30	5.33	0%	102.2°
2031-05-21 Wed	98	—	unknown	00:25–04:00 (good, 3.58 h)	71.1° 05:25	5.28	0%	111.6°
2031-05-22 Thu	98	—	unknown	00:20–03:55 (good, 3.58 h)	71.1° 05:20	5.23	2%	120.5°
2031-05-23 Fri	100	—	unknown	00:15–03:55 (good, 3.67 h)	71.1° 05:15	5.18	6%	128.6°
2031-05-24 Sat	100	—	unknown	00:10–03:55 (good, 3.75 h)	71.1° 05:15	5.14	12%	135.4°
2031-05-25 Sun	100	—	unknown	00:10–03:55 (good, 3.75 h)	71.1° 05:10	5.09	18%	140.4°
2031-05-26 Mon	100	—	unknown	00:05–03:50 (good, 3.75 h)	71.1° 05:05	5.05	26%	142.7°
2031-05-27 Tue	100	—	unknown	00:05–03:50 (good, 3.75 h)	71.1° 05:00	5.0	35%	141.9°
2031-05-28 Wed	100	—	unknown	00:00–03:50 (good, 3.83 h)	71.1° 04:55	4.96	45%	138.0°
2031-05-29 Thu	100	—	unknown	23:55–03:50 (good, 3.92 h)	71.1° 04:55	4.92	55%	131.7°
2031-05-30 Fri	100	—	unknown	23:55–03:45 (good, 3.83 h)	71.1° 04:50	4.88	65%	123.5°
2031-05-31 Sat	100	—	unknown	23:55–03:45 (good, 3.83 h)	71.1° 04:45	4.84	74%	114.1°
2031-06-01 Sun	98	—	unknown	23:55–03:45 (good, 3.83 h)	71.1° 04:40	4.8	83%	103.7°
2031-06-02 Mon	75	—	unknown	00:00–03:45 (good, 3.75 h)	71.1° 04:40	4.77	91%	92.6°
2031-06-03 Tue	62	—	unknown	00:50–03:45 (good, 2.92 h)	71.1° 04:35	4.73	96%	81.1°
2031-06-04 Wed	50	—	unknown	01:55–03:45 (good, 1.83 h)	71.1° 04:30	4.7	100%	69.5°
2031-06-05 Thu	40	—	unknown	23:10–03:40 (marginal, 4.5 h)	71.1° 04:25	4.67	100%	58.4°
2031-06-06 Fri	34	—	unknown	23:05–03:40 (marginal, 4.58 h)	71.1° 04:20	4.64	97%	48.5°
2031-06-07 Sat	34	—	unknown	23:05–03:40 (marginal, 4.58 h)	71.1° 04:20	4.61	91%	41.0°
2031-06-08 Sun	58	—	unknown	23:15–23:40 (good, 0.42 h)	71.1° 04:15	4.59	83%	37.4°
2031-06-09 Mon	72	—	unknown	23:10–03:15 (good, 4.08 h)	71.1° 04:10	4.56	74%	38.5°
2031-06-10 Tue	86	—	unknown	23:05–03:40 (good, 4.58 h)	71.1° 04:05	4.54	63%	43.6°
2031-06-11 Wed	94	—	unknown	23:10–03:40 (good, 4.5 h)	71.1° 04:00	4.52	52%	51.4°
2031-06-12 Thu	98	—	unknown	23:10–03:40 (good, 4.5 h)	71.1° 04:00	4.5	41%	60.5°
2031-06-13 Fri	100	—	unknown	23:10–03:40 (good, 4.5 h)	71.1° 03:55	4.48	31%	70.2°
2031-06-14 Sat	100	—	unknown	23:10–03:40 (good, 4.5 h)	71.1° 03:50	4.47	22%	80.1°
2031-06-15 Sun	100	—	unknown	23:10–03:40 (good, 4.5 h)	71.1° 03:45	4.46	14%	90.0°
2031-06-16 Mon	100	—	unknown	23:10–03:40 (good, 4.5 h)	71.1° 03:45	4.44	8%	99.8°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2031-05-18&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.