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: 12-25 (18), 12-26 (18), 12-23 (17), 12-24 (17), 12-22 (16) — by astronomy; check the weather when the night is within four days.

2026-12-20astronomy score per night — click a bar for that night2027-01-18

night of	astronomy	weather	overall	best window	highest	dark h	Moon	Moon sep.
2026-12-20 Sun	14	—	unknown	18:35–18:40 (good, 0.08 h)	71.1° 14:25	11.51	86%	91.4°
2026-12-21 Mon	15	—	unknown	18:35–19:05 (good, 0.5 h)	71.1° 14:25	11.51	93%	102.0°
2026-12-22 Tue	16	—	unknown	18:35–19:10 (good, 0.58 h)	71.1° 14:20	11.51	98%	112.4°
2026-12-23 Wed	17	—	unknown	18:40–19:10 (good, 0.5 h)	71.1° 14:15	11.51	100%	122.1°
2026-12-24 Thu	17	—	unknown	18:40–19:10 (good, 0.5 h)	71.1° 14:10	11.5	99%	130.1°
2026-12-25 Fri	18	—	unknown	18:40–19:05 (good, 0.42 h)	71.1° 14:05	11.5	95%	135.4°
2026-12-26 Sat	18	—	unknown	18:40–19:10 (good, 0.5 h)	71.1° 14:05	11.5	88%	136.8°
2026-12-27 Sun	16	—	unknown	18:40–19:05 (good, 0.42 h)	71.1° 14:00	11.49	79%	134.3°
2026-12-28 Mon	15	—	unknown	18:40–19:00 (good, 0.33 h)	71.1° 13:55	11.49	70%	128.8°
2026-12-29 Tue	12	—	unknown	18:40–18:55 (good, 0.25 h)	71.1° 13:50	11.48	59%	121.4°
2026-12-30 Wed	11	—	unknown	18:40–18:55 (good, 0.25 h)	71.1° 13:45	11.47	48%	113.0°
2026-12-31 Thu	8	—	unknown	18:45–18:50 (good, 0.08 h)	71.1° 13:45	11.46	38%	104.2°
2027-01-01 Fri	8	—	unknown	18:10–19:15 (marginal, 1.08 h)	71.1° 13:40	11.45	29%	95.2°
2027-01-02 Sat	7	—	unknown	18:45–19:10 (marginal, 0.42 h)	71.1° 13:35	11.44	20%	86.2°
2027-01-03 Sun	6	—	unknown	18:10–18:40 (marginal, 0.5 h)	71.1° 13:30	11.43	13%	77.5°
2027-01-04 Mon	5	—	unknown	18:10–18:35 (marginal, 0.42 h)	71.1° 13:30	11.42	8%	69.1°
2027-01-05 Tue	3	—	unknown	18:15–18:30 (marginal, 0.25 h)	71.1° 13:25	11.41	3%	61.3°
2027-01-06 Wed	3	—	unknown	18:15–18:25 (marginal, 0.17 h)	71.1° 13:20	11.39	1%	54.4°
2027-01-07 Thu	2	—	unknown	18:15–18:20 (marginal, 0.08 h)	71.1° 13:15	11.38	0%	48.6°
2027-01-08 Fri	1	—	unknown	18:15–18:20 (marginal, 0.08 h)	71.1° 13:10	11.36	1%	44.7°
2027-01-09 Sat	1	—	unknown	—	71.1° 13:10	11.35	4%	43.1°
2027-01-10 Sun	1	—	unknown	—	71.1° 13:05	11.33	8%	44.0°
2027-01-11 Mon	1	—	unknown	—	71.1° 13:00	11.31	14%	47.5°
2027-01-12 Tue	0	—	unknown	—	71.1° 12:55	11.29	22%	53.1°
2027-01-13 Wed	0	—	unknown	—	71.1° 12:50	11.27	31%	60.3°
2027-01-14 Thu	0	—	unknown	—	71.1° 12:50	11.25	40%	68.6°
2027-01-15 Fri	0	—	unknown	—	71.1° 12:45	11.23	51%	77.7°
2027-01-16 Sat	0	—	unknown	—	71.1° 12:40	11.21	62%	87.5°
2027-01-17 Sun	0	—	unknown	—	71.1° 12:35	11.19	72%	97.6°
2027-01-18 Mon	0	—	unknown	—	71.1° 12:30	11.16	82%	107.9°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2026-12-20&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.