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: 09-28 (59), 09-29 (58), 09-27 (57), 09-30 (57), 09-26 (56) — by astronomy; check the weather when the night is within four days.

2028-09-05astronomy score per night — click a bar for that night2028-10-04

night of	astronomy	weather	overall	best window	highest	dark h	Moon	Moon sep.
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°
2028-09-21 Thu	48	—	unknown	03:35–05:40 (good, 2.08 h)	42.9° 06:50	8.71	14%	129.7°
2028-09-22 Fri	48	—	unknown	03:35–05:40 (good, 2.08 h)	42.9° 06:50	8.76	23%	139.5°
2028-09-23 Sat	50	—	unknown	03:30–05:40 (good, 2.17 h)	42.9° 06:45	8.81	33%	146.4°
2028-09-24 Sun	52	—	unknown	03:25–05:40 (good, 2.25 h)	42.9° 06:40	8.86	44%	149.1°
2028-09-25 Mon	55	—	unknown	03:20–05:45 (good, 2.42 h)	42.9° 06:35	8.91	54%	147.0°
2028-09-26 Tue	56	—	unknown	03:20–05:45 (good, 2.42 h)	42.9° 06:30	8.96	64%	141.3°
2028-09-27 Wed	57	—	unknown	03:15–05:45 (good, 2.5 h)	42.9° 06:30	9.01	73%	133.4°
2028-09-28 Thu	59	—	unknown	03:10–05:45 (good, 2.58 h)	42.9° 06:25	9.06	81%	124.3°
2028-09-29 Fri	58	—	unknown	03:15–05:45 (good, 2.5 h)	42.9° 06:20	9.11	88%	114.7°
2028-09-30 Sat	57	—	unknown	03:20–05:50 (good, 2.5 h)	42.9° 06:15	9.16	93%	104.8°
2028-10-01 Sun	43	—	unknown	03:30–05:50 (good, 2.33 h)	42.9° 06:10	9.2	97%	94.7°
2028-10-02 Mon	35	—	unknown	04:35–05:50 (good, 1.25 h)	42.9° 06:10	9.25	99%	84.5°
2028-10-03 Tue	27	—	unknown	02:40–05:50 (marginal, 3.17 h)	42.9° 06:05	9.3	100%	74.4°
2028-10-04 Wed	21	—	unknown	02:50–05:55 (marginal, 3.08 h)	42.9° 06:00	9.35	98%	64.4°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2028-09-05&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.