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 (45), 09-19 (43), 09-18 (42), 09-17 (41), 09-16 (38) — by astronomy; check the weather when the night is within four days.

2028-08-22astronomy score per night — click a bar for that night2028-09-20

night of	astronomy	weather	overall	best window	highest	dark h	Moon	Moon sep.
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°
2028-09-10 Sun	9	—	unknown	04:10–05:25 (marginal, 1.25 h)	42.9° 07:35	8.13	61%	36.3°
2028-09-11 Mon	12	—	unknown	03:55–05:25 (marginal, 1.5 h)	42.9° 07:30	8.19	51%	31.8°
2028-09-12 Tue	16	—	unknown	03:40–05:25 (marginal, 1.75 h)	42.9° 07:25	8.24	41%	31.5°
2028-09-13 Wed	22	—	unknown	04:30–05:30 (good, 1.0 h)	42.9° 07:25	8.29	30%	36.1°
2028-09-14 Thu	28	—	unknown	04:15–05:30 (good, 1.25 h)	42.9° 07:20	8.35	20%	44.4°
2028-09-15 Fri	33	—	unknown	04:05–05:30 (good, 1.42 h)	42.9° 07:15	8.4	12%	55.0°
2028-09-16 Sat	38	—	unknown	03:55–05:30 (good, 1.58 h)	42.9° 07:10	8.45	5%	67.0°
2028-09-17 Sun	41	—	unknown	03:55–05:35 (good, 1.67 h)	42.9° 07:05	8.5	1%	79.8°
2028-09-18 Mon	42	—	unknown	03:50–05:35 (good, 1.75 h)	42.9° 07:05	8.56	0%	92.8°
2028-09-19 Tue	43	—	unknown	03:45–05:35 (good, 1.83 h)	42.9° 07:00	8.61	2%	105.8°
2028-09-20 Wed	45	—	unknown	03:40–05:35 (good, 1.92 h)	42.9° 06:55	8.66	7%	118.3°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2028-08-22&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.