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: 04-21 (93), 04-22 (93), 04-23 (93), 04-24 (93), 04-25 (93) — by astronomy; check the weather when the night is within four days.

2031-04-21astronomy score per night — click a bar for that night2031-05-20

night of	astronomy	weather	overall	best window	highest	dark h	Moon	Moon sep.
2031-04-21 Mon	93	—	unknown	21:55–03:45 (good, 5.83 h)	50.2° 23:55	6.96	0%	150.8°
2031-04-22 Tue	93	—	unknown	21:55–03:40 (good, 5.75 h)	50.2° 23:50	6.9	2%	138.7°
2031-04-23 Wed	93	—	unknown	21:55–03:35 (good, 5.67 h)	50.2° 23:45	6.84	5%	126.6°
2031-04-24 Thu	93	—	unknown	22:00–03:35 (good, 5.58 h)	50.2° 23:40	6.78	10%	114.6°
2031-04-25 Fri	93	—	unknown	22:00–03:30 (good, 5.5 h)	50.2° 23:35	6.72	16%	102.8°
2031-04-26 Sat	92	—	unknown	22:00–03:25 (good, 5.42 h)	50.2° 23:35	6.67	24%	91.0°
2031-04-27 Sun	89	—	unknown	22:05–03:20 (good, 5.25 h)	50.2° 23:30	6.61	32%	79.3°
2031-04-28 Mon	86	—	unknown	22:05–03:15 (good, 5.17 h)	50.2° 23:25	6.55	42%	67.6°
2031-04-29 Tue	82	—	unknown	22:05–03:15 (good, 5.17 h)	50.2° 23:20	6.49	51%	55.9°
2031-04-30 Wed	65	—	unknown	22:55–02:45 (good, 3.83 h)	50.2° 23:15	6.43	61%	44.0°
2031-05-01 Thu	41	—	unknown	22:10–03:35 (marginal, 5.42 h)	50.2° 23:15	6.38	70%	32.0°
2031-05-02 Fri	31	—	unknown	22:10–03:20 (marginal, 5.17 h)	50.2° 23:10	6.32	79%	20.2°
2031-05-03 Sat	24	—	unknown	22:10–03:10 (marginal, 5.0 h)	50.2° 23:05	6.26	87%	10.2°
2031-05-04 Sun	19	—	unknown	22:15–02:55 (marginal, 4.67 h)	50.2° 23:00	6.2	94%	12.3°
2031-05-05 Mon	18	—	unknown	22:15–02:40 (marginal, 4.42 h)	50.2° 23:00	6.14	98%	24.1°
2031-05-06 Tue	25	—	unknown	22:15–02:40 (marginal, 4.42 h)	50.2° 22:55	6.09	100%	37.8°
2031-05-07 Wed	37	—	unknown	22:20–02:50 (marginal, 4.5 h)	50.2° 22:50	6.03	99%	52.0°
2031-05-08 Thu	53	—	unknown	22:20–00:25 (good, 2.08 h)	50.2° 22:45	5.97	96%	66.5°
2031-05-09 Fri	84	—	unknown	22:20–01:55 (good, 3.58 h)	50.2° 22:40	5.92	89%	81.1°
2031-05-10 Sat	91	—	unknown	22:25–02:10 (good, 3.75 h)	50.2° 22:40	5.86	81%	95.6°
2031-05-11 Sun	93	—	unknown	22:25–02:15 (good, 3.83 h)	50.2° 22:35	5.81	71%	109.9°
2031-05-12 Mon	93	—	unknown	22:25–02:15 (good, 3.83 h)	50.2° 22:30	5.75	60%	123.9°
2031-05-13 Tue	92	—	unknown	22:30–02:15 (good, 3.75 h)	50.2° 22:25	5.7	48%	137.6°
2031-05-14 Wed	91	—	unknown	22:30–02:15 (good, 3.75 h)	50.2° 22:20	5.64	38%	150.8°
2031-05-15 Thu	89	—	unknown	22:30–02:10 (good, 3.67 h)	50.2° 22:20	5.59	27%	163.0°
2031-05-16 Fri	86	—	unknown	22:35–02:05 (good, 3.5 h)	50.2° 22:15	5.54	18%	171.0°
2031-05-17 Sat	85	—	unknown	22:35–02:05 (good, 3.5 h)	50.2° 22:10	5.48	11%	165.4°
2031-05-18 Sun	83	—	unknown	22:35–02:00 (good, 3.42 h)	50.2° 22:05	5.43	6%	154.2°
2031-05-19 Mon	80	—	unknown	22:40–01:55 (good, 3.25 h)	50.2° 22:05	5.38	2%	142.2°
2031-05-20 Tue	78	—	unknown	22:40–01:50 (good, 3.17 h)	50.2° 22:00	5.33	0%	130.2°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2031-04-21&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.