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: 05-31 (100), 06-01 (100), 06-02 (100), 06-03 (100), 06-04 (100) — by astronomy; check the weather when the night is within four days.

2027-05-23astronomy score per night — click a bar for that night2027-06-21

night of	astronomy	weather	overall	best window	highest	dark h	Moon	Moon sep.
2027-05-23 Sun	39	—	unknown	03:10–03:55 (good, 0.75 h)	71.1° 05:15	5.19	89%	51.1°
2027-05-24 Mon	49	—	unknown	02:20–03:55 (good, 1.58 h)	71.1° 05:15	5.14	82%	46.0°
2027-05-25 Tue	63	—	unknown	00:10–03:55 (good, 3.75 h)	71.1° 05:10	5.09	74%	43.0°
2027-05-26 Wed	71	—	unknown	00:05–03:50 (good, 3.75 h)	71.1° 05:05	5.05	66%	42.6°
2027-05-27 Thu	80	—	unknown	00:00–03:50 (good, 3.83 h)	71.1° 05:00	5.0	56%	44.8°
2027-05-28 Fri	89	—	unknown	23:55–03:50 (good, 3.92 h)	71.1° 04:55	4.96	47%	49.3°
2027-05-29 Sat	96	—	unknown	23:50–03:50 (good, 4.0 h)	71.1° 04:55	4.92	37%	55.7°
2027-05-30 Sun	99	—	unknown	23:50–03:45 (good, 3.92 h)	71.1° 04:50	4.88	27%	63.6°
2027-05-31 Mon	100	—	unknown	23:45–03:45 (good, 4.0 h)	71.1° 04:45	4.84	19%	72.5°
2027-06-01 Tue	100	—	unknown	23:40–03:45 (good, 4.08 h)	71.1° 04:40	4.8	11%	82.2°
2027-06-02 Wed	100	—	unknown	23:35–03:45 (good, 4.17 h)	71.1° 04:40	4.77	5%	92.4°
2027-06-03 Thu	100	—	unknown	23:35–03:45 (good, 4.17 h)	71.1° 04:35	4.73	1%	102.9°
2027-06-04 Fri	100	—	unknown	23:30–03:45 (good, 4.25 h)	71.1° 04:30	4.7	0%	113.1°
2027-06-05 Sat	100	—	unknown	23:25–03:40 (good, 4.25 h)	71.1° 04:25	4.67	2%	122.7°
2027-06-06 Sun	100	—	unknown	23:20–03:40 (good, 4.33 h)	71.1° 04:20	4.64	6%	130.6°
2027-06-07 Mon	100	—	unknown	23:20–03:40 (good, 4.33 h)	71.1° 04:20	4.61	14%	136.0°
2027-06-08 Tue	100	—	unknown	23:15–03:40 (good, 4.42 h)	71.1° 04:15	4.59	23%	137.7°
2027-06-09 Wed	100	—	unknown	23:10–03:40 (good, 4.5 h)	71.1° 04:10	4.56	33%	135.4°
2027-06-10 Thu	100	—	unknown	23:10–03:40 (good, 4.5 h)	71.1° 04:05	4.54	44%	129.9°
2027-06-11 Fri	100	—	unknown	23:10–03:40 (good, 4.5 h)	71.1° 04:00	4.52	55%	122.4°
2027-06-12 Sat	100	—	unknown	23:10–03:40 (good, 4.5 h)	71.1° 04:00	4.5	66%	113.7°
2027-06-13 Sun	100	—	unknown	23:10–03:40 (good, 4.5 h)	71.1° 03:55	4.48	76%	104.5°
2027-06-14 Mon	100	—	unknown	23:10–03:40 (good, 4.5 h)	71.1° 03:50	4.47	84%	95.1°
2027-06-15 Tue	100	—	unknown	23:20–03:40 (good, 4.33 h)	71.1° 03:45	4.45	91%	85.7°
2027-06-16 Wed	71	—	unknown	00:05–03:40 (good, 3.58 h)	71.1° 03:45	4.44	96%	76.5°
2027-06-17 Thu	59	—	unknown	00:50–03:40 (good, 2.83 h)	71.1° 03:40	4.44	99%	67.8°
2027-06-18 Fri	50	—	unknown	01:40–03:40 (good, 2.0 h)	71.1° 03:35	4.43	100%	59.8°
2027-06-19 Sat	44	—	unknown	23:10–03:40 (marginal, 4.5 h)	71.1° 03:30	4.42	99%	52.8°
2027-06-20 Sun	41	—	unknown	23:15–03:40 (marginal, 4.42 h)	71.1° 03:25	4.42	97%	47.1°
2027-06-21 Mon	43	—	unknown	23:15–03:40 (marginal, 4.42 h)	71.1° 03:25	4.42	92%	43.5°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2027-05-23&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.