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: 09-03 (100), 09-04 (100), 09-05 (100), 09-06 (100), 09-07 (100) — by astronomy; check the weather when the night is within four days.

2040-09-01astronomy score per night — click a bar for that night2040-09-30

night of	astronomy	weather	overall	best window	highest	dark h	Moon	Moon sep.
2040-09-01 Sat	89	—	unknown	01:15–05:15 (good, 4.0 h)	72.5° 06:20	7.65	19%	48.2°
2040-09-02 Sun	96	—	unknown	01:10–05:15 (good, 4.08 h)	72.5° 06:20	7.7	12%	60.0°
2040-09-03 Mon	100	—	unknown	01:10–05:15 (good, 4.08 h)	72.5° 06:15	7.76	7%	71.8°
2040-09-04 Tue	100	—	unknown	01:05–05:15 (good, 4.17 h)	72.5° 06:10	7.81	3%	83.8°
2040-09-05 Wed	100	—	unknown	01:00–05:20 (good, 4.33 h)	72.5° 06:05	7.87	1%	95.8°
2040-09-06 Thu	100	—	unknown	00:55–05:20 (good, 4.42 h)	72.5° 06:05	7.92	0%	108.1°
2040-09-07 Fri	100	—	unknown	00:55–05:20 (good, 4.42 h)	72.5° 06:00	7.98	2%	120.5°
2040-09-08 Sat	100	—	unknown	00:50–05:20 (good, 4.5 h)	72.5° 05:55	8.03	5%	133.1°
2040-09-09 Sun	100	—	unknown	00:45–05:25 (good, 4.67 h)	72.5° 05:50	8.08	11%	145.9°
2040-09-10 Mon	100	—	unknown	00:40–05:25 (good, 4.75 h)	72.5° 05:45	8.14	18%	158.8°
2040-09-11 Tue	100	—	unknown	00:35–05:25 (good, 4.83 h)	72.5° 05:45	8.19	27%	171.5°
2040-09-12 Wed	100	—	unknown	00:35–05:25 (good, 4.83 h)	72.5° 05:40	8.25	37%	173.0°
2040-09-13 Thu	100	—	unknown	00:30–05:30 (good, 5.0 h)	72.5° 05:35	8.3	48%	160.0°
2040-09-14 Fri	100	—	unknown	00:25–05:30 (good, 5.08 h)	72.5° 05:30	8.35	60%	146.1°
2040-09-15 Sat	100	—	unknown	00:25–05:30 (good, 5.08 h)	72.5° 05:25	8.4	70%	131.9°
2040-09-16 Sun	100	—	unknown	00:25–05:30 (good, 5.08 h)	72.5° 05:25	8.46	80%	117.5°
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°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2040-09-01&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.