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: 04-29 (93), 04-30 (93), 05-01 (93), 05-02 (93), 05-03 (93) — by astronomy; check the weather when the night is within four days.

2040-04-26astronomy score per night — click a bar for that night2040-05-25

night of	astronomy	weather	overall	best window	highest	dark h	Moon	Moon sep.
2040-04-26 Thu	21	—	unknown	22:00–03:00 (marginal, 5.0 h)	50.1° 23:30	6.62	100%	29.1°
2040-04-27 Fri	35	—	unknown	22:05–03:15 (marginal, 5.17 h)	50.1° 23:25	6.56	99%	43.3°
2040-04-28 Sat	78	—	unknown	22:05–23:50 (good, 1.75 h)	50.1° 23:25	6.5	96%	57.7°
2040-04-29 Sun	93	—	unknown	22:05–01:55 (good, 3.83 h)	50.1° 23:20	6.44	90%	72.2°
2040-04-30 Mon	93	—	unknown	22:10–02:45 (good, 4.58 h)	50.1° 23:15	6.39	81%	86.8°
2040-05-01 Tue	93	—	unknown	22:10–02:50 (good, 4.67 h)	50.1° 23:10	6.33	71%	101.2°
2040-05-02 Wed	93	—	unknown	22:10–02:55 (good, 4.75 h)	50.1° 23:05	6.27	60%	115.5°
2040-05-03 Thu	93	—	unknown	22:15–02:55 (good, 4.67 h)	50.1° 23:05	6.21	49%	129.6°
2040-05-04 Fri	93	—	unknown	22:15–02:50 (good, 4.58 h)	50.1° 23:00	6.16	38%	143.5°
2040-05-05 Sat	93	—	unknown	22:15–02:45 (good, 4.5 h)	50.1° 22:55	6.1	27%	157.2°
2040-05-06 Sun	93	—	unknown	22:20–02:45 (good, 4.42 h)	50.1° 22:50	6.04	18%	170.7°
2040-05-07 Mon	93	—	unknown	22:20–02:40 (good, 4.33 h)	50.1° 22:45	5.98	11%	176.0°
2040-05-08 Tue	93	—	unknown	22:20–02:35 (good, 4.25 h)	50.1° 22:45	5.93	5%	162.9°
2040-05-09 Wed	93	—	unknown	22:25–02:30 (good, 4.08 h)	50.1° 22:40	5.87	2%	150.1°
2040-05-10 Thu	93	—	unknown	22:25–02:25 (good, 4.0 h)	50.1° 22:35	5.82	0%	137.4°
2040-05-11 Fri	93	—	unknown	22:25–02:25 (good, 4.0 h)	50.1° 22:30	5.76	1%	125.0°
2040-05-12 Sat	92	—	unknown	22:30–02:20 (good, 3.83 h)	50.1° 22:25	5.71	3%	112.8°
2040-05-13 Sun	91	—	unknown	22:30–02:15 (good, 3.75 h)	50.1° 22:25	5.65	7%	100.7°
2040-05-14 Mon	86	—	unknown	22:30–02:10 (good, 3.67 h)	50.1° 22:20	5.6	13%	88.7°
2040-05-15 Tue	78	—	unknown	22:35–02:05 (good, 3.5 h)	50.1° 22:15	5.55	20%	76.9°
2040-05-16 Wed	69	—	unknown	22:35–02:05 (good, 3.5 h)	50.1° 22:10	5.49	28%	65.0°
2040-05-17 Thu	58	—	unknown	22:35–01:45 (good, 3.17 h)	50.1° 22:10	5.44	37%	53.2°
2040-05-18 Fri	45	—	unknown	22:40–01:35 (good, 2.92 h)	50.1° 22:05	5.39	46%	41.2°
2040-05-19 Sat	32	—	unknown	22:40–02:20 (marginal, 3.67 h)	50.1° 22:00	5.34	56%	29.0°
2040-05-20 Sun	25	—	unknown	22:40–02:10 (marginal, 3.5 h)	50.1° 21:55	5.29	66%	16.6°
2040-05-21 Mon	18	—	unknown	22:45–01:55 (marginal, 3.17 h)	50.1° 21:50	5.24	75%	3.7°
2040-05-22 Tue	14	—	unknown	22:45–01:45 (marginal, 3.0 h)	50.1° 21:50	5.19	84%	9.5°
2040-05-23 Wed	12	—	unknown	22:45–01:25 (marginal, 2.67 h)	50.1° 21:45	5.15	91%	23.2°
2040-05-24 Thu	14	—	unknown	22:45–01:25 (marginal, 2.67 h)	50.1° 21:40	5.1	97%	37.3°
2040-05-25 Fri	20	—	unknown	22:50–01:35 (marginal, 2.75 h)	50.1° 21:35	5.05	100%	51.8°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2040-04-26&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.