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 3C 273: 04-19 (93), 04-20 (93), 04-21 (93), 04-22 (93), 04-23 (93) — by astronomy; check the weather when the night is within four days.

2041-04-16astronomy score per night — click a bar for that night2041-05-15

night of	astronomy	weather	overall	best window	highest	dark h	Moon	Moon sep.
2041-04-16 Tue	26	—	unknown	21:45–03:40 (marginal, 5.92 h)	50.1° 00:10	7.21	100%	26.7°
2041-04-17 Wed	41	—	unknown	21:50–03:55 (marginal, 6.08 h)	50.1° 00:05	7.16	98%	39.6°
2041-04-18 Thu	90	—	unknown	21:50–23:50 (good, 2.0 h)	50.1° 00:05	7.1	94%	52.7°
2041-04-19 Fri	93	—	unknown	21:50–02:15 (good, 4.42 h)	50.1° 00:00	7.04	88%	66.0°
2041-04-20 Sat	93	—	unknown	21:55–03:20 (good, 5.42 h)	50.1° 23:55	6.98	79%	79.5°
2041-04-21 Sun	93	—	unknown	21:55–03:30 (good, 5.58 h)	50.1° 23:50	6.92	70%	93.2°
2041-04-22 Mon	93	—	unknown	21:55–03:30 (good, 5.58 h)	50.1° 23:45	6.87	59%	107.1°
2041-04-23 Tue	93	—	unknown	21:55–03:35 (good, 5.67 h)	50.1° 23:45	6.81	48%	121.2°
2041-04-24 Wed	93	—	unknown	22:00–03:30 (good, 5.5 h)	50.1° 23:40	6.75	36%	135.4°
2041-04-25 Thu	93	—	unknown	22:00–03:25 (good, 5.42 h)	50.1° 23:35	6.69	26%	149.7°
2041-04-26 Fri	93	—	unknown	22:00–03:25 (good, 5.42 h)	50.1° 23:30	6.63	16%	164.0°
2041-04-27 Sat	93	—	unknown	22:05–03:20 (good, 5.25 h)	50.1° 23:25	6.57	8%	177.9°
2041-04-28 Sun	93	—	unknown	22:05–03:15 (good, 5.17 h)	50.1° 23:25	6.52	3%	167.1°
2041-04-29 Mon	93	—	unknown	22:05–03:10 (good, 5.08 h)	50.1° 23:20	6.46	0%	153.0°
2041-04-30 Tue	93	—	unknown	22:10–03:05 (good, 4.92 h)	50.1° 23:15	6.4	0%	139.1°
2041-05-01 Wed	93	—	unknown	22:10–03:05 (good, 4.92 h)	50.1° 23:10	6.34	2%	125.5°
2041-05-02 Thu	93	—	unknown	22:10–03:00 (good, 4.83 h)	50.1° 23:10	6.28	7%	112.2°
2041-05-03 Fri	92	—	unknown	22:15–02:55 (good, 4.67 h)	50.1° 23:05	6.23	13%	99.3°
2041-05-04 Sat	89	—	unknown	22:15–02:50 (good, 4.58 h)	50.1° 23:00	6.17	21%	86.7°
2041-05-05 Sun	84	—	unknown	22:15–02:50 (good, 4.58 h)	50.1° 22:55	6.11	29%	74.5°
2041-05-06 Mon	75	—	unknown	22:20–02:45 (good, 4.42 h)	50.1° 22:50	6.05	38%	62.4°
2041-05-07 Tue	60	—	unknown	22:20–02:20 (good, 4.0 h)	50.1° 22:50	6.0	48%	50.5°
2041-05-08 Wed	45	—	unknown	23:25–01:40 (good, 2.25 h)	50.1° 22:45	5.94	57%	38.7°
2041-05-09 Thu	32	—	unknown	22:25–02:55 (marginal, 4.5 h)	50.1° 22:40	5.89	66%	26.8°
2041-05-10 Fri	25	—	unknown	22:25–02:45 (marginal, 4.33 h)	50.1° 22:35	5.83	75%	14.9°
2041-05-11 Sat	19	—	unknown	22:25–02:30 (marginal, 4.08 h)	50.1° 22:30	5.77	83%	3.1°
2041-05-12 Sun	16	—	unknown	22:30–02:20 (marginal, 3.83 h)	50.1° 22:30	5.72	90%	9.8°
2041-05-13 Mon	14	—	unknown	22:30–02:05 (marginal, 3.58 h)	50.1° 22:25	5.67	95%	22.3°
2041-05-14 Tue	18	—	unknown	22:30–02:00 (marginal, 3.5 h)	50.1° 22:20	5.61	99%	35.3°
2041-05-15 Wed	26	—	unknown	22:35–02:10 (marginal, 3.58 h)	50.1° 22:15	5.56	100%	48.5°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2041-04-16&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.