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 Seven Sisters: 09-17 (100), 09-18 (100), 10-01 (100), 10-02 (100), 10-03 (100) — by astronomy; check the weather when the night is within four days.

2040-09-17astronomy score per night — click a bar for that night2040-10-16

night of	astronomy	weather	overall	best window	highest	dark h	Moon	Moon sep.
2040-09-17 Mon	100	—	unknown	00:30–05:35 (good, 5.08 h)	72.5° 05:20	8.51	89%	102.9°
2040-09-18 Tue	100	—	unknown	01:00–05:35 (good, 4.58 h)	72.5° 05:15	8.56	95%	88.3°
2040-09-19 Wed	67	—	unknown	02:35–05:35 (good, 3.0 h)	72.5° 05:10	8.61	99%	73.7°
2040-09-20 Thu	46	—	unknown	00:00–06:10 (marginal, 6.17 h)	72.5° 05:10	8.66	100%	59.2°
2040-09-21 Fri	30	—	unknown	00:10–05:40 (marginal, 5.5 h)	72.5° 05:05	8.71	98%	45.1°
2040-09-22 Sat	19	—	unknown	00:15–05:40 (marginal, 5.42 h)	72.5° 05:00	8.77	94%	31.3°
2040-09-23 Sun	20	—	unknown	23:55–05:40 (marginal, 5.75 h)	72.5° 04:55	8.82	88%	18.1°
2040-09-24 Mon	27	—	unknown	23:40–05:40 (marginal, 6.0 h)	72.5° 04:50	8.87	80%	6.0°
2040-09-25 Tue	38	—	unknown	23:25–05:45 (marginal, 6.33 h)	72.5° 04:50	8.92	71%	8.9°
2040-09-26 Wed	54	—	unknown	23:10–05:45 (marginal, 6.58 h)	72.5° 04:45	8.97	62%	20.7°
2040-09-27 Thu	68	—	unknown	00:00–05:45 (good, 5.75 h)	72.5° 04:40	9.01	53%	32.6°
2040-09-28 Fri	82	—	unknown	23:30–05:45 (good, 6.25 h)	72.5° 04:35	9.06	43%	44.5°
2040-09-29 Sat	89	—	unknown	23:25–05:45 (good, 6.33 h)	72.5° 04:30	9.11	34%	56.3°
2040-09-30 Sun	97	—	unknown	23:20–05:50 (good, 6.5 h)	72.5° 04:30	9.16	25%	68.1°
2040-10-01 Mon	100	—	unknown	23:20–05:50 (good, 6.5 h)	72.5° 04:25	9.21	18%	80.0°
2040-10-02 Tue	100	—	unknown	23:15–05:50 (good, 6.58 h)	72.5° 04:20	9.26	11%	92.0°
2040-10-03 Wed	100	—	unknown	23:10–05:50 (good, 6.67 h)	72.5° 04:15	9.3	6%	104.2°
2040-10-04 Thu	100	—	unknown	23:05–05:55 (good, 6.83 h)	72.5° 04:15	9.35	2%	116.7°
2040-10-05 Fri	100	—	unknown	23:05–05:55 (good, 6.83 h)	72.5° 04:10	9.4	0%	129.4°
2040-10-06 Sat	100	—	unknown	23:00–05:55 (good, 6.92 h)	72.5° 04:05	9.44	1%	142.3°
2040-10-07 Sun	100	—	unknown	22:55–05:55 (good, 7.0 h)	72.5° 04:00	9.49	3%	155.4°
2040-10-08 Mon	100	—	unknown	22:50–05:55 (good, 7.08 h)	72.5° 03:55	9.54	8%	168.5°
2040-10-09 Tue	100	—	unknown	22:45–06:00 (good, 7.25 h)	72.5° 03:55	9.58	15%	175.4°
2040-10-10 Wed	100	—	unknown	22:45–06:00 (good, 7.25 h)	72.5° 03:50	9.63	24%	163.1°
2040-10-11 Thu	100	—	unknown	22:40–06:00 (good, 7.33 h)	72.5° 03:45	9.67	34%	149.4°
2040-10-12 Fri	100	—	unknown	22:40–06:00 (good, 7.33 h)	72.5° 03:40	9.72	45%	135.4°
2040-10-13 Sat	100	—	unknown	22:35–06:05 (good, 7.5 h)	72.5° 03:35	9.76	56%	121.4°
2040-10-14 Sun	100	—	unknown	22:40–06:05 (good, 7.42 h)	72.5° 03:35	9.8	68%	107.2°
2040-10-15 Mon	100	—	unknown	22:45–06:05 (good, 7.33 h)	72.5° 03:30	9.85	78%	93.0°
2040-10-16 Tue	100	—	unknown	23:35–06:05 (good, 6.5 h)	72.5° 03:25	9.89	87%	78.8°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2040-09-17&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.