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: 02-17 (93), 02-18 (93), 02-19 (93), 02-20 (93), 03-05 (93) — by astronomy; check the weather when the night is within four days.

2040-02-17astronomy score per night — click a bar for that night2040-03-17

night of	astronomy	weather	overall	best window	highest	dark h	Moon	Moon sep.
2040-02-17 Fri	93	—	unknown	23:15–05:45 (good, 6.5 h)	50.1° 03:00	10.18	31%	149.1°
2040-02-18 Sat	93	—	unknown	23:15–05:40 (good, 6.42 h)	50.1° 03:00	10.14	41%	136.6°
2040-02-19 Sun	93	—	unknown	23:10–05:40 (good, 6.5 h)	50.1° 02:55	10.1	50%	124.5°
2040-02-20 Mon	93	—	unknown	23:15–05:40 (good, 6.42 h)	50.1° 02:50	10.06	60%	112.5°
2040-02-21 Tue	92	—	unknown	23:20–05:35 (good, 6.25 h)	50.1° 02:45	10.02	69%	100.6°
2040-02-22 Wed	89	—	unknown	23:35–05:35 (good, 6.0 h)	50.1° 02:40	9.97	77%	88.8°
2040-02-23 Thu	85	—	unknown	01:05–05:35 (good, 4.5 h)	50.1° 02:40	9.93	84%	77.0°
2040-02-24 Fri	60	—	unknown	03:45–05:35 (good, 1.83 h)	50.1° 02:35	9.89	91%	65.0°
2040-02-25 Sat	42	—	unknown	23:00–05:30 (marginal, 6.5 h)	50.1° 02:30	9.84	96%	52.9°
2040-02-26 Sun	28	—	unknown	01:10–05:30 (marginal, 4.33 h)	50.1° 02:25	9.8	99%	40.5°
2040-02-27 Mon	19	—	unknown	03:30–05:30 (marginal, 2.0 h)	50.1° 02:20	9.75	100%	28.0°
2040-02-28 Tue	18	—	unknown	03:45–05:25 (marginal, 1.67 h)	50.1° 02:20	9.71	99%	15.3°
2040-02-29 Wed	20	—	unknown	22:45–05:25 (marginal, 6.67 h)	50.1° 02:15	9.66	96%	2.3°
2040-03-01 Thu	29	—	unknown	22:15–05:25 (marginal, 7.17 h)	50.1° 02:10	9.62	91%	10.9°
2040-03-02 Fri	42	—	unknown	21:50–05:20 (marginal, 7.5 h)	50.1° 02:05	9.57	84%	24.3°
2040-03-03 Sat	83	—	unknown	22:15–23:15 (good, 1.0 h)	50.1° 02:05	9.53	75%	37.8°
2040-03-04 Sun	90	—	unknown	22:10–04:20 (good, 6.17 h)	50.1° 02:00	9.48	65%	51.5°
2040-03-05 Mon	93	—	unknown	22:10–05:15 (good, 7.08 h)	50.1° 01:55	9.43	54%	65.4°
2040-03-06 Tue	93	—	unknown	22:05–05:15 (good, 7.17 h)	50.1° 01:50	9.39	43%	79.5°
2040-03-07 Wed	93	—	unknown	22:00–05:15 (good, 7.25 h)	50.1° 01:45	9.34	32%	93.7°
2040-03-08 Thu	93	—	unknown	21:55–05:10 (good, 7.25 h)	50.1° 01:45	9.29	22%	108.1°
2040-03-09 Fri	93	—	unknown	21:50–05:10 (good, 7.33 h)	50.1° 01:40	9.24	13%	122.5°
2040-03-10 Sat	93	—	unknown	21:50–05:10 (good, 7.33 h)	50.1° 01:35	9.19	6%	136.9°
2040-03-11 Sun	93	—	unknown	21:45–05:05 (good, 7.33 h)	50.1° 01:30	9.15	2%	151.2°
2040-03-12 Mon	93	—	unknown	21:40–05:05 (good, 7.42 h)	50.1° 01:25	9.1	0%	165.3°
2040-03-13 Tue	93	—	unknown	21:35–05:05 (good, 7.5 h)	50.1° 01:25	9.05	1%	179.1°
2040-03-14 Wed	93	—	unknown	21:35–05:00 (good, 7.42 h)	50.1° 01:20	9.0	4%	167.3°
2040-03-15 Thu	93	—	unknown	21:30–05:00 (good, 7.5 h)	50.1° 01:15	8.95	10%	154.1°
2040-03-16 Fri	93	—	unknown	21:25–05:00 (good, 7.58 h)	50.1° 01:10	8.9	16%	141.3°
2040-03-17 Sat	93	—	unknown	21:25–04:55 (good, 7.5 h)	50.1° 01:10	8.84	24%	128.8°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2040-02-17&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.