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: 05-21 (74), 05-22 (73), 05-23 (71), 05-24 (69), 05-25 (66) — by astronomy; check the weather when the night is within four days.

2028-05-21astronomy score per night — click a bar for that night2028-06-19

night of	astronomy	weather	overall	best window	highest	dark h	Moon	Moon sep.
2028-05-21 Sun	74	—	unknown	22:45–01:45 (good, 3.0 h)	50.2° 21:50	5.24	6%	151.8°
2028-05-22 Mon	73	—	unknown	22:45–01:40 (good, 2.92 h)	50.2° 21:50	5.2	2%	139.7°
2028-05-23 Tue	71	—	unknown	22:45–01:35 (good, 2.83 h)	50.2° 21:45	5.15	0%	127.0°
2028-05-24 Wed	69	—	unknown	22:45–01:30 (good, 2.75 h)	50.2° 21:40	5.1	0%	113.9°
2028-05-25 Thu	66	—	unknown	22:50–01:30 (good, 2.67 h)	50.2° 21:35	5.06	3%	100.6°
2028-05-26 Fri	63	—	unknown	22:50–01:25 (good, 2.58 h)	50.2° 21:30	5.01	8%	87.0°
2028-05-27 Sat	59	—	unknown	22:50–01:20 (good, 2.5 h)	50.2° 21:30	4.97	15%	73.3°
2028-05-28 Sun	51	—	unknown	22:55–01:15 (good, 2.33 h)	50.2° 21:25	4.93	24%	59.5°
2028-05-29 Mon	42	—	unknown	22:55–01:10 (good, 2.25 h)	50.2° 21:20	4.89	34%	45.7°
2028-05-30 Tue	32	—	unknown	22:55–00:45 (good, 1.83 h)	50.2° 21:15	4.85	46%	32.0°
2028-05-31 Wed	25	—	unknown	22:55–01:35 (marginal, 2.67 h)	50.2° 21:15	4.81	57%	19.0°
2028-06-01 Thu	19	—	unknown	23:00–01:25 (marginal, 2.42 h)	50.2° 21:10	4.78	68%	9.9°
2028-06-02 Fri	14	—	unknown	23:00–01:10 (marginal, 2.17 h)	50.2° 21:05	4.74	78%	15.2°
2028-06-03 Sat	12	—	unknown	23:00–01:00 (marginal, 2.0 h)	50.2° 21:00	4.71	87%	27.4°
2028-06-04 Sun	12	—	unknown	23:00–00:55 (marginal, 1.92 h)	50.2° 20:55	4.68	93%	40.7°
2028-06-05 Mon	15	—	unknown	23:05–00:55 (marginal, 1.83 h)	50.2° 20:55	4.65	98%	54.0°
2028-06-06 Tue	18	—	unknown	23:05–01:00 (marginal, 1.92 h)	50.2° 20:50	4.62	100%	67.3°
2028-06-07 Wed	22	—	unknown	23:05–23:40 (good, 0.58 h)	50.2° 20:45	4.59	99%	80.3°
2028-06-08 Thu	27	—	unknown	23:05–00:10 (good, 1.08 h)	50.2° 20:40	4.57	97%	93.0°
2028-06-09 Fri	35	—	unknown	23:05–00:15 (good, 1.17 h)	50.2° 20:35	4.54	92%	105.5°
2028-06-10 Sat	36	—	unknown	23:05–00:15 (good, 1.17 h)	50.2° 20:35	4.52	86%	117.7°
2028-06-11 Sun	34	—	unknown	23:10–00:15 (good, 1.08 h)	50.2° 20:30	4.5	79%	129.6°
2028-06-12 Mon	33	—	unknown	23:10–00:15 (good, 1.08 h)	50.2° 20:25	4.49	71%	141.2°
2028-06-13 Tue	32	—	unknown	23:10–00:15 (good, 1.08 h)	50.2° 20:20	4.47	62%	152.5°
2028-06-14 Wed	30	—	unknown	23:10–00:10 (good, 1.0 h)	50.2° 20:20	4.46	52%	163.0°
2028-06-15 Thu	29	—	unknown	23:10–00:05 (good, 0.92 h)	50.2° 20:15	4.45	43%	170.0°
2028-06-16 Fri	27	—	unknown	23:10–00:00 (good, 0.83 h)	50.2° 20:10	4.44	34%	166.1°
2028-06-17 Sat	26	—	unknown	23:10–00:00 (good, 0.83 h)	50.2° 20:05	4.43	25%	155.8°
2028-06-18 Sun	25	—	unknown	23:10–23:55 (good, 0.75 h)	50.2° 20:00	4.43	16%	144.1°
2028-06-19 Mon	24	—	unknown	23:10–23:50 (good, 0.67 h)	50.2° 20:00	4.42	10%	131.6°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2028-05-21&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.