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), 05-21 (98) — by astronomy; check the weather when the night is within four days.

2039-04-27astronomy score per night — click a bar for that night2039-05-26

night of	astronomy	weather	overall	best window	highest	dark h	Moon	Moon sep.
2039-04-27 Wed	71	—	unknown	02:00–04:40 (good, 2.67 h)	71.1° 07:00	6.6	17%	123.2°
2039-04-28 Thu	71	—	unknown	01:55–04:35 (good, 2.67 h)	71.1° 06:55	6.55	25%	128.6°
2039-04-29 Fri	72	—	unknown	01:55–04:35 (good, 2.67 h)	71.1° 06:50	6.49	34%	132.5°
2039-04-30 Sat	73	—	unknown	01:50–04:35 (good, 2.75 h)	71.1° 06:50	6.43	43%	134.2°
2039-05-01 Sun	72	—	unknown	01:45–04:30 (good, 2.75 h)	71.1° 06:45	6.37	53%	133.3°
2039-05-02 Mon	73	—	unknown	01:45–04:30 (good, 2.75 h)	71.1° 06:40	6.31	64%	129.9°
2039-05-03 Tue	73	—	unknown	01:40–04:30 (good, 2.83 h)	71.1° 06:35	6.26	74%	124.1°
2039-05-04 Wed	64	—	unknown	01:40–04:25 (good, 2.75 h)	71.1° 06:30	6.2	83%	116.4°
2039-05-05 Thu	58	—	unknown	01:45–04:25 (good, 2.67 h)	71.1° 06:30	6.14	91%	107.4°
2039-05-06 Fri	50	—	unknown	01:50–04:20 (good, 2.5 h)	71.1° 06:25	6.08	96%	97.5°
2039-05-07 Sat	43	—	unknown	02:30–04:20 (good, 1.83 h)	71.1° 06:20	6.03	100%	87.1°
2039-05-08 Sun	37	—	unknown	03:10–04:20 (good, 1.17 h)	71.1° 06:15	5.97	100%	76.6°
2039-05-09 Mon	33	—	unknown	03:45–04:15 (good, 0.5 h)	71.1° 06:10	5.91	97%	66.7°
2039-05-10 Tue	33	—	unknown	03:55–04:15 (good, 0.33 h)	71.1° 06:10	5.86	91%	57.9°
2039-05-11 Wed	36	—	unknown	03:20–04:15 (good, 0.92 h)	71.1° 06:05	5.8	83%	51.1°
2039-05-12 Thu	50	—	unknown	01:00–04:10 (good, 3.17 h)	71.1° 06:00	5.75	74%	46.9°
2039-05-13 Fri	64	—	unknown	00:55–04:10 (good, 3.25 h)	71.1° 05:55	5.69	63%	45.9°
2039-05-14 Sat	74	—	unknown	00:50–04:10 (good, 3.33 h)	71.1° 05:55	5.64	52%	48.1°
2039-05-15 Sun	82	—	unknown	00:45–04:05 (good, 3.33 h)	71.1° 05:50	5.59	42%	52.7°
2039-05-16 Mon	89	—	unknown	00:45–04:05 (good, 3.33 h)	71.1° 05:45	5.53	32%	59.0°
2039-05-17 Tue	93	—	unknown	00:40–04:05 (good, 3.42 h)	71.1° 05:40	5.48	23%	66.3°
2039-05-18 Wed	94	—	unknown	00:35–04:05 (good, 3.5 h)	71.1° 05:35	5.43	15%	74.3°
2039-05-19 Thu	94	—	unknown	00:30–04:00 (good, 3.5 h)	71.1° 05:35	5.38	9%	82.5°
2039-05-20 Fri	96	—	unknown	00:30–04:00 (good, 3.5 h)	71.1° 05:30	5.33	4%	90.8°
2039-05-21 Sat	98	—	unknown	00:25–04:00 (good, 3.58 h)	71.1° 05:25	5.28	1%	99.1°
2039-05-22 Sun	98	—	unknown	00:20–03:55 (good, 3.58 h)	71.1° 05:20	5.23	0%	107.1°
2039-05-23 Mon	100	—	unknown	00:15–03:55 (good, 3.67 h)	71.1° 05:15	5.18	1%	114.6°
2039-05-24 Tue	100	—	unknown	00:10–03:55 (good, 3.75 h)	71.1° 05:15	5.13	3%	121.5°
2039-05-25 Wed	100	—	unknown	00:10–03:55 (good, 3.75 h)	71.1° 05:10	5.09	7%	127.3°
2039-05-26 Thu	100	—	unknown	00:05–03:50 (good, 3.75 h)	71.1° 05:05	5.04	13%	131.6°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2039-04-27&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.