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 Great Orion Nebula: 09-17 (40), 09-16 (38), 09-18 (38), 09-15 (36), 09-14 (35) — by astronomy; check the weather when the night is within four days.

2040-08-30astronomy score per night — click a bar for that night2040-09-28

night of	astronomy	weather	overall	best window	highest	dark h	Moon	Moon sep.
2040-08-30 Thu	5	—	unknown	04:35–05:10 (marginal, 0.58 h)	42.9° 08:20	7.53	36%	30.9°
2040-08-31 Fri	7	—	unknown	04:30–05:10 (marginal, 0.67 h)	42.9° 08:15	7.59	27%	34.2°
2040-09-01 Sat	11	—	unknown	05:05–05:15 (good, 0.17 h)	42.9° 08:10	7.65	19%	40.5°
2040-09-02 Sun	13	—	unknown	05:00–05:15 (good, 0.25 h)	42.9° 08:05	7.7	12%	48.5°
2040-09-03 Mon	16	—	unknown	04:50–05:15 (good, 0.42 h)	42.9° 08:05	7.76	7%	57.6°
2040-09-04 Tue	17	—	unknown	04:45–05:15 (good, 0.5 h)	42.9° 08:00	7.81	3%	67.4°
2040-09-05 Wed	21	—	unknown	04:40–05:20 (good, 0.67 h)	42.9° 07:55	7.87	1%	77.6°
2040-09-06 Thu	22	—	unknown	04:35–05:20 (good, 0.75 h)	42.9° 07:50	7.92	0%	88.1°
2040-09-07 Fri	24	—	unknown	04:35–05:20 (good, 0.75 h)	42.9° 07:45	7.98	2%	98.8°
2040-09-08 Sat	24	—	unknown	04:30–05:20 (good, 0.83 h)	42.9° 07:45	8.03	5%	109.6°
2040-09-09 Sun	27	—	unknown	04:25–05:25 (good, 1.0 h)	42.9° 07:40	8.08	11%	120.1°
2040-09-10 Mon	28	—	unknown	04:20–05:25 (good, 1.08 h)	42.9° 07:35	8.14	18%	130.3°
2040-09-11 Tue	30	—	unknown	04:15–05:25 (good, 1.17 h)	42.9° 07:30	8.19	27%	139.4°
2040-09-12 Wed	31	—	unknown	04:15–05:25 (good, 1.17 h)	42.9° 07:25	8.25	37%	146.3°
2040-09-13 Thu	33	—	unknown	04:10–05:30 (good, 1.33 h)	42.9° 07:25	8.3	48%	149.2°
2040-09-14 Fri	35	—	unknown	04:05–05:30 (good, 1.42 h)	42.9° 07:20	8.35	60%	146.7°
2040-09-15 Sat	36	—	unknown	04:00–05:30 (good, 1.5 h)	42.9° 07:15	8.4	70%	139.5°
2040-09-16 Sun	38	—	unknown	03:55–05:30 (good, 1.58 h)	42.9° 07:10	8.46	80%	129.5°
2040-09-17 Mon	40	—	unknown	03:55–05:35 (good, 1.67 h)	42.9° 07:10	8.51	89%	118.0°
2040-09-18 Tue	38	—	unknown	04:05–05:35 (good, 1.5 h)	42.9° 07:05	8.56	95%	105.8°
2040-09-19 Wed	27	—	unknown	04:15–05:35 (good, 1.33 h)	42.9° 07:00	8.61	99%	93.3°
2040-09-20 Thu	22	—	unknown	05:25–05:35 (good, 0.17 h)	42.9° 06:55	8.66	100%	80.9°
2040-09-21 Fri	17	—	unknown	03:30–05:40 (marginal, 2.17 h)	42.9° 06:50	8.71	98%	68.9°
2040-09-22 Sat	12	—	unknown	03:40–05:40 (marginal, 2.0 h)	42.9° 06:50	8.77	94%	57.6°
2040-09-23 Sun	10	—	unknown	03:45–05:40 (marginal, 1.92 h)	42.9° 06:45	8.82	88%	47.4°
2040-09-24 Mon	10	—	unknown	03:40–05:40 (marginal, 2.0 h)	42.9° 06:40	8.87	80%	38.9°
2040-09-25 Tue	12	—	unknown	03:25–05:45 (marginal, 2.33 h)	42.9° 06:35	8.92	71%	33.0°
2040-09-26 Wed	16	—	unknown	03:05–05:45 (marginal, 2.67 h)	42.9° 06:30	8.97	62%	30.9°
2040-09-27 Thu	22	—	unknown	02:50–05:45 (marginal, 2.92 h)	42.9° 06:30	9.01	53%	33.0°
2040-09-28 Fri	30	—	unknown	03:45–05:45 (good, 2.0 h)	42.9° 06:25	9.06	43%	38.5°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2040-08-30&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.