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: 12-16 (33), 12-17 (31), 12-18 (27), 12-19 (23), 12-20 (19) — by astronomy; check the weather when the night is within four days.

2039-12-16astronomy score per night — click a bar for that night2040-01-14

night of	astronomy	weather	overall	best window	highest	dark h	Moon	Moon sep.
2039-12-16 Fri	33	—	unknown	18:35–19:50 (good, 1.25 h)	71.1° 14:45	11.5	2%	50.7°
2039-12-17 Sat	31	—	unknown	18:35–19:45 (good, 1.17 h)	71.1° 14:40	11.5	8%	47.0°
2039-12-18 Sun	27	—	unknown	18:35–19:35 (good, 1.0 h)	71.1° 14:35	11.5	15%	46.8°
2039-12-19 Mon	23	—	unknown	18:35–19:30 (good, 0.92 h)	71.1° 14:30	11.51	24%	50.0°
2039-12-20 Tue	19	—	unknown	18:35–19:20 (good, 0.75 h)	71.1° 14:30	11.51	34%	55.6°
2039-12-21 Wed	16	—	unknown	18:35–19:10 (good, 0.58 h)	71.1° 14:25	11.51	45%	62.7°
2039-12-22 Thu	14	—	unknown	18:35–19:00 (good, 0.42 h)	71.1° 14:20	11.51	55%	70.6°
2039-12-23 Fri	12	—	unknown	18:40–18:45 (good, 0.08 h)	71.1° 14:15	11.51	65%	78.9°
2039-12-24 Sat	11	—	unknown	18:40–18:45 (good, 0.08 h)	71.1° 14:10	11.5	74%	87.4°
2039-12-25 Sun	11	—	unknown	18:40–18:50 (good, 0.17 h)	71.1° 14:10	11.5	82%	95.7°
2039-12-26 Mon	11	—	unknown	18:40–18:50 (good, 0.17 h)	71.1° 14:05	11.5	89%	103.9°
2039-12-27 Tue	11	—	unknown	18:40–18:50 (good, 0.17 h)	71.1° 14:00	11.49	94%	111.6°
2039-12-28 Wed	11	—	unknown	18:40–18:50 (good, 0.17 h)	71.1° 13:55	11.49	98%	118.7°
2039-12-29 Thu	10	—	unknown	18:40–18:50 (good, 0.17 h)	71.1° 13:50	11.48	100%	124.8°
2039-12-30 Fri	9	—	unknown	18:40–18:45 (good, 0.08 h)	71.1° 13:50	11.47	100%	129.7°
2039-12-31 Sat	8	—	unknown	18:10–19:20 (marginal, 1.17 h)	71.1° 13:45	11.46	98%	132.7°
2040-01-01 Sun	8	—	unknown	18:10–19:15 (marginal, 1.08 h)	71.1° 13:40	11.45	95%	133.5°
2040-01-02 Mon	7	—	unknown	18:10–19:10 (marginal, 1.0 h)	71.1° 13:35	11.44	90%	132.0°
2040-01-03 Tue	6	—	unknown	18:10–18:40 (marginal, 0.5 h)	71.1° 13:35	11.43	83%	128.3°
2040-01-04 Wed	5	—	unknown	18:10–18:35 (marginal, 0.42 h)	71.1° 13:30	11.42	75%	122.7°
2040-01-05 Thu	4	—	unknown	18:45–19:00 (marginal, 0.25 h)	71.1° 13:25	11.41	66%	115.7°
2040-01-06 Fri	3	—	unknown	18:45–18:55 (marginal, 0.17 h)	71.1° 13:20	11.39	56%	107.7°
2040-01-07 Sat	2	—	unknown	18:15–18:25 (marginal, 0.17 h)	71.1° 13:15	11.38	45%	98.8°
2040-01-08 Sun	2	—	unknown	18:15–18:20 (marginal, 0.08 h)	71.1° 13:15	11.36	34%	89.4°
2040-01-09 Mon	1	—	unknown	—	71.1° 13:10	11.35	24%	79.8°
2040-01-10 Tue	1	—	unknown	—	71.1° 13:05	11.33	15%	70.2°
2040-01-11 Wed	1	—	unknown	—	71.1° 13:00	11.31	7%	61.2°
2040-01-12 Thu	1	—	unknown	—	71.1° 12:55	11.29	2%	53.6°
2040-01-13 Fri	0	—	unknown	—	71.1° 12:55	11.27	0%	48.3°
2040-01-14 Sat	0	—	unknown	—	71.1° 12:50	11.25	1%	46.4°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2039-12-16&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.