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: 09-01 (13), 09-02 (11), 09-03 (11), 08-31 (10), 08-29 (9) — by astronomy; check the weather when the night is within four days.

2028-08-11astronomy score per night — click a bar for that night2028-09-09

night of	astronomy	weather	overall	best window	highest	dark h	Moon	Moon sep.
2028-08-11 Fri	0	—	unknown	—	42.9° 09:35	6.44	65%	59.5°
2028-08-12 Sat	0	—	unknown	—	42.9° 09:30	6.5	56%	50.1°
2028-08-13 Sun	0	—	unknown	—	42.9° 09:25	6.56	46%	41.5°
2028-08-14 Mon	0	—	unknown	—	42.9° 09:20	6.61	35%	34.7°
2028-08-15 Tue	0	—	unknown	—	42.9° 09:15	6.67	26%	31.3°
2028-08-16 Wed	0	—	unknown	—	42.9° 09:15	6.73	16%	32.9°
2028-08-17 Thu	0	—	unknown	—	42.9° 09:10	6.79	9%	39.2°
2028-08-18 Fri	0	—	unknown	—	42.9° 09:05	6.84	3%	48.8°
2028-08-19 Sat	1	—	unknown	—	42.9° 09:00	6.9	0%	60.3°
2028-08-20 Sun	1	—	unknown	—	42.9° 08:55	6.96	0%	72.8°
2028-08-21 Mon	1	—	unknown	—	42.9° 08:55	7.02	4%	85.7°
2028-08-22 Tue	1	—	unknown	—	42.9° 08:50	7.07	9%	98.6°
2028-08-23 Wed	2	—	unknown	05:30–05:35 (marginal, 0.08 h)	42.9° 08:45	7.13	17%	111.1°
2028-08-24 Thu	3	—	unknown	05:30–05:40 (marginal, 0.17 h)	42.9° 08:40	7.19	27%	122.8°
2028-08-25 Fri	4	—	unknown	05:25–05:40 (marginal, 0.25 h)	42.9° 08:40	7.25	38%	133.3°
2028-08-26 Sat	4	—	unknown	04:50–05:05 (marginal, 0.25 h)	42.9° 08:35	7.3	49%	141.9°
2028-08-27 Sun	5	—	unknown	04:45–05:05 (marginal, 0.33 h)	42.9° 08:30	7.36	59%	147.5°
2028-08-28 Mon	7	—	unknown	05:10–05:45 (marginal, 0.58 h)	42.9° 08:25	7.42	69%	148.8°
2028-08-29 Tue	9	—	unknown	04:35–05:45 (marginal, 1.17 h)	42.9° 08:20	7.47	78%	145.6°
2028-08-30 Wed	9	—	unknown	05:05–05:10 (good, 0.08 h)	42.9° 08:20	7.53	86%	139.2°
2028-08-31 Thu	10	—	unknown	05:00–05:10 (good, 0.17 h)	42.9° 08:15	7.58	92%	131.0°
2028-09-01 Fri	13	—	unknown	05:05–05:15 (good, 0.17 h)	42.9° 08:10	7.64	96%	121.8°
2028-09-02 Sat	11	—	unknown	05:05–05:15 (good, 0.17 h)	42.9° 08:05	7.7	99%	112.1°
2028-09-03 Sun	11	—	unknown	05:10–05:15 (good, 0.08 h)	42.9° 08:00	7.75	100%	102.1°
2028-09-04 Mon	9	—	unknown	04:15–05:15 (marginal, 1.0 h)	42.9° 08:00	7.81	99%	92.0°
2028-09-05 Tue	9	—	unknown	04:20–05:20 (marginal, 1.0 h)	42.9° 07:55	7.86	96%	81.9°
2028-09-06 Wed	8	—	unknown	04:25–05:20 (marginal, 0.92 h)	42.9° 07:50	7.92	92%	71.9°
2028-09-07 Thu	7	—	unknown	04:25–05:20 (marginal, 0.92 h)	42.9° 07:45	7.97	86%	62.0°
2028-09-08 Fri	6	—	unknown	04:25–05:20 (marginal, 0.92 h)	42.9° 07:45	8.03	79%	52.5°
2028-09-09 Sat	7	—	unknown	04:20–05:25 (marginal, 1.08 h)	42.9° 07:40	8.08	71%	43.7°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2028-08-11&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.