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: 09-20 (44), 09-19 (43), 09-18 (41), 09-17 (38), 09-16 (37) — by astronomy; check the weather when the night is within four days.

2031-08-22astronomy score per night — click a bar for that night2031-09-20

night of	astronomy	weather	overall	best window	highest	dark h	Moon	Moon sep.
2031-08-22 Fri	1	—	unknown	—	42.9° 08:55	7.03	21%	116.0°
2031-08-23 Sat	1	—	unknown	—	42.9° 08:50	7.09	30%	127.2°
2031-08-24 Sun	2	—	unknown	05:30–05:40 (marginal, 0.17 h)	42.9° 08:45	7.15	41%	137.9°
2031-08-25 Mon	3	—	unknown	05:25–05:40 (marginal, 0.25 h)	42.9° 08:40	7.2	52%	147.2°
2031-08-26 Tue	4	—	unknown	04:50–05:05 (marginal, 0.25 h)	42.9° 08:35	7.26	63%	153.2°
2031-08-27 Wed	5	—	unknown	04:50–05:05 (marginal, 0.25 h)	42.9° 08:35	7.32	74%	152.9°
2031-08-28 Thu	6	—	unknown	05:15–05:45 (marginal, 0.5 h)	42.9° 08:30	7.37	83%	146.3°
2031-08-29 Fri	8	—	unknown	04:40–05:45 (marginal, 1.08 h)	42.9° 08:25	7.43	91%	135.8°
2031-08-30 Sat	8	—	unknown	04:35–05:10 (marginal, 0.58 h)	42.9° 08:20	7.49	97%	123.7°
2031-08-31 Sun	7	—	unknown	04:30–05:10 (marginal, 0.67 h)	42.9° 08:15	7.54	100%	110.8°
2031-09-01 Mon	6	—	unknown	04:30–05:10 (marginal, 0.67 h)	42.9° 08:15	7.6	99%	97.7°
2031-09-02 Tue	6	—	unknown	04:30–05:15 (marginal, 0.75 h)	42.9° 08:10	7.66	97%	84.8°
2031-09-03 Wed	5	—	unknown	04:35–05:15 (marginal, 0.67 h)	42.9° 08:05	7.71	92%	72.3°
2031-09-04 Thu	5	—	unknown	04:40–05:15 (marginal, 0.58 h)	42.9° 08:00	7.77	84%	60.4°
2031-09-05 Fri	5	—	unknown	04:40–05:15 (marginal, 0.58 h)	42.9° 07:55	7.82	76%	49.3°
2031-09-06 Sat	6	—	unknown	04:30–05:20 (marginal, 0.83 h)	42.9° 07:55	7.88	67%	39.4°
2031-09-07 Sun	7	—	unknown	04:20–05:20 (marginal, 1.0 h)	42.9° 07:50	7.93	57%	31.4°
2031-09-08 Mon	10	—	unknown	04:05–05:20 (marginal, 1.25 h)	42.9° 07:45	7.99	48%	26.6°
2031-09-09 Tue	14	—	unknown	05:15–05:20 (good, 0.08 h)	42.9° 07:40	8.04	38%	26.5°
2031-09-10 Wed	18	—	unknown	04:45–05:25 (good, 0.67 h)	42.9° 07:40	8.09	29%	31.0°
2031-09-11 Thu	23	—	unknown	04:30–05:25 (good, 0.92 h)	42.9° 07:35	8.15	21%	38.4°
2031-09-12 Fri	27	—	unknown	04:20–05:25 (good, 1.08 h)	42.9° 07:30	8.2	14%	47.4°
2031-09-13 Sat	30	—	unknown	04:10–05:25 (good, 1.25 h)	42.9° 07:25	8.26	8%	57.4°
2031-09-14 Sun	34	—	unknown	04:10–05:30 (good, 1.33 h)	42.9° 07:20	8.31	4%	68.0°
2031-09-15 Mon	35	—	unknown	04:05–05:30 (good, 1.42 h)	42.9° 07:20	8.36	1%	79.0°
2031-09-16 Tue	37	—	unknown	04:00–05:30 (good, 1.5 h)	42.9° 07:15	8.41	0%	90.2°
2031-09-17 Wed	38	—	unknown	03:55–05:30 (good, 1.58 h)	42.9° 07:10	8.47	2%	101.7°
2031-09-18 Thu	41	—	unknown	03:50–05:35 (good, 1.75 h)	42.9° 07:05	8.52	5%	113.3°
2031-09-19 Fri	43	—	unknown	03:50–05:35 (good, 1.75 h)	42.9° 07:00	8.57	10%	124.7°
2031-09-20 Sat	44	—	unknown	03:45–05:35 (good, 1.83 h)	42.9° 07:00	8.62	18%	135.7°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2031-08-22&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.