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: 09-09 (25), 09-08 (24), 09-07 (22), 09-06 (21), 09-05 (18) — by astronomy; check the weather when the night is within four days.

2027-08-11astronomy score per night — click a bar for that night2027-09-09

night of	astronomy	weather	overall	best window	highest	dark h	Moon	Moon sep.
2027-08-11 Wed	0	—	unknown	—	42.9° 09:35	6.4	76%	147.1°
2027-08-12 Thu	0	—	unknown	—	42.9° 09:30	6.46	84%	146.7°
2027-08-13 Fri	0	—	unknown	—	42.9° 09:30	6.51	90%	142.8°
2027-08-14 Sat	0	—	unknown	—	42.9° 09:25	6.57	95%	136.3°
2027-08-15 Sun	0	—	unknown	—	42.9° 09:20	6.63	98%	128.2°
2027-08-16 Mon	0	—	unknown	—	42.9° 09:15	6.69	100%	119.2°
2027-08-17 Tue	0	—	unknown	—	42.9° 09:10	6.74	100%	109.6°
2027-08-18 Wed	0	—	unknown	—	42.9° 09:10	6.8	98%	99.6°
2027-08-19 Thu	0	—	unknown	—	42.9° 09:05	6.86	94%	89.4°
2027-08-20 Fri	0	—	unknown	—	42.9° 09:00	6.92	88%	79.1°
2027-08-21 Sat	0	—	unknown	—	42.9° 08:55	6.97	81%	68.8°
2027-08-22 Sun	0	—	unknown	—	42.9° 08:50	7.03	72%	58.7°
2027-08-23 Mon	1	—	unknown	—	42.9° 08:50	7.09	62%	49.1°
2027-08-24 Tue	1	—	unknown	—	42.9° 08:45	7.15	52%	40.6°
2027-08-25 Wed	2	—	unknown	—	42.9° 08:40	7.2	41%	34.5°
2027-08-26 Thu	3	—	unknown	04:50–05:05 (marginal, 0.25 h)	42.9° 08:35	7.26	30%	32.6°
2027-08-27 Fri	4	—	unknown	04:50–05:05 (marginal, 0.25 h)	42.9° 08:35	7.32	20%	36.0°
2027-08-28 Sat	5	—	unknown	04:45–05:05 (marginal, 0.33 h)	42.9° 08:30	7.37	11%	43.7°
2027-08-29 Sun	7	—	unknown	04:40–05:45 (marginal, 1.08 h)	42.9° 08:25	7.43	5%	54.1°
2027-08-30 Mon	9	—	unknown	05:05–05:10 (good, 0.08 h)	42.9° 08:20	7.49	1%	65.9°
2027-08-31 Tue	10	—	unknown	05:05–05:10 (good, 0.08 h)	42.9° 08:15	7.54	0%	78.3°
2027-09-01 Wed	11	—	unknown	05:00–05:10 (good, 0.17 h)	42.9° 08:15	7.6	2%	90.8°
2027-09-02 Thu	14	—	unknown	04:55–05:15 (good, 0.33 h)	42.9° 08:10	7.65	7%	103.0°
2027-09-03 Fri	15	—	unknown	04:50–05:15 (good, 0.42 h)	42.9° 08:05	7.71	14%	114.6°
2027-09-04 Sat	17	—	unknown	04:45–05:15 (good, 0.5 h)	42.9° 08:00	7.76	22%	125.3°
2027-09-05 Sun	18	—	unknown	04:45–05:15 (good, 0.5 h)	42.9° 07:55	7.82	32%	134.7°
2027-09-06 Mon	21	—	unknown	04:40–05:20 (good, 0.67 h)	42.9° 07:55	7.87	42%	142.1°
2027-09-07 Tue	22	—	unknown	04:35–05:20 (good, 0.75 h)	42.9° 07:50	7.93	52%	146.6°
2027-09-08 Wed	24	—	unknown	04:30–05:20 (good, 0.83 h)	42.9° 07:45	7.98	61%	147.3°
2027-09-09 Thu	25	—	unknown	04:30–05:20 (good, 0.83 h)	42.9° 07:40	8.04	70%	144.3°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2027-08-11&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.