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: 04-26 (93), 04-27 (93), 05-12 (92), 05-13 (92), 05-14 (91) — by astronomy; check the weather when the night is within four days.

2039-04-26astronomy score per night — click a bar for that night2039-05-25

night of	astronomy	weather	overall	best window	highest	dark h	Moon	Moon sep.
2039-04-26 Tue	93	—	unknown	22:00–03:25 (good, 5.42 h)	50.1° 23:35	6.66	11%	110.9°
2039-04-27 Wed	93	—	unknown	22:05–03:20 (good, 5.25 h)	50.1° 23:30	6.6	17%	99.0°
2039-04-28 Thu	90	—	unknown	22:05–03:15 (good, 5.17 h)	50.1° 23:25	6.55	25%	87.1°
2039-04-29 Fri	85	—	unknown	22:05–03:15 (good, 5.17 h)	50.1° 23:20	6.49	34%	75.1°
2039-04-30 Sat	80	—	unknown	22:10–03:10 (good, 5.0 h)	50.1° 23:20	6.43	43%	62.9°
2039-05-01 Sun	62	—	unknown	22:10–02:45 (good, 4.58 h)	50.1° 23:15	6.37	53%	50.3°
2039-05-02 Mon	44	—	unknown	22:10–03:30 (marginal, 5.33 h)	50.1° 23:10	6.31	64%	37.5°
2039-05-03 Tue	30	—	unknown	22:10–03:15 (marginal, 5.08 h)	50.1° 23:05	6.26	74%	24.2°
2039-05-04 Wed	22	—	unknown	22:15–03:05 (marginal, 4.83 h)	50.1° 23:00	6.2	83%	10.4°
2039-05-05 Thu	17	—	unknown	22:15–02:45 (marginal, 4.5 h)	50.1° 23:00	6.14	91%	3.9°
2039-05-06 Fri	15	—	unknown	22:15–02:25 (marginal, 4.17 h)	50.1° 22:55	6.08	96%	18.6°
2039-05-07 Sat	19	—	unknown	22:20–02:20 (marginal, 4.0 h)	50.1° 22:50	6.03	100%	33.6°
2039-05-08 Sun	31	—	unknown	22:20–02:40 (marginal, 4.33 h)	50.1° 22:45	5.97	100%	48.8°
2039-05-09 Mon	48	—	unknown	22:20–23:55 (good, 1.58 h)	50.1° 22:40	5.91	97%	64.0°
2039-05-10 Tue	82	—	unknown	22:25–01:40 (good, 3.25 h)	50.1° 22:40	5.86	91%	79.0°
2039-05-11 Wed	90	—	unknown	22:25–02:05 (good, 3.67 h)	50.1° 22:35	5.8	83%	93.8°
2039-05-12 Thu	92	—	unknown	22:25–02:15 (good, 3.83 h)	50.1° 22:30	5.75	74%	108.2°
2039-05-13 Fri	92	—	unknown	22:30–02:15 (good, 3.75 h)	50.1° 22:25	5.69	63%	122.1°
2039-05-14 Sat	91	—	unknown	22:30–02:15 (good, 3.75 h)	50.1° 22:25	5.64	52%	135.7°
2039-05-15 Sun	89	—	unknown	22:30–02:10 (good, 3.67 h)	50.1° 22:20	5.59	42%	148.8°
2039-05-16 Mon	86	—	unknown	22:35–02:05 (good, 3.5 h)	50.1° 22:15	5.53	32%	161.6°
2039-05-17 Tue	85	—	unknown	22:35–02:05 (good, 3.5 h)	50.1° 22:10	5.48	23%	174.1°
2039-05-18 Wed	83	—	unknown	22:35–02:00 (good, 3.42 h)	50.1° 22:05	5.43	15%	173.6°
2039-05-19 Thu	80	—	unknown	22:40–01:55 (good, 3.25 h)	50.1° 22:05	5.38	9%	161.5°
2039-05-20 Fri	78	—	unknown	22:40–01:50 (good, 3.17 h)	50.1° 22:00	5.33	4%	149.5°
2039-05-21 Sat	77	—	unknown	22:40–01:45 (good, 3.08 h)	50.1° 21:55	5.28	1%	137.6°
2039-05-22 Sun	74	—	unknown	22:45–01:45 (good, 3.0 h)	50.1° 21:50	5.23	0%	125.7°
2039-05-23 Mon	72	—	unknown	22:45–01:40 (good, 2.92 h)	50.1° 21:45	5.18	1%	113.9°
2039-05-24 Tue	71	—	unknown	22:45–01:35 (good, 2.83 h)	50.1° 21:45	5.13	3%	102.1°
2039-05-25 Wed	67	—	unknown	22:50–01:30 (good, 2.67 h)	50.1° 21:40	5.09	7%	90.2°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2039-04-26&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.