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: 05-16 (69), 05-17 (58), 05-29 (57), 05-30 (56), 05-31 (55) — by astronomy; check the weather when the night is within four days.

2040-05-16astronomy score per night — click a bar for that night2040-06-14

night of	astronomy	weather	overall	best window	highest	dark h	Moon	Moon sep.
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°
2040-05-26 Sat	28	—	unknown	22:50–23:00 (good, 0.17 h)	50.1° 21:30	5.01	100%	66.6°
2040-05-27 Sun	38	—	unknown	22:50–00:35 (good, 1.75 h)	50.1° 21:30	4.97	97%	81.5°
2040-05-28 Mon	54	—	unknown	22:55–01:00 (good, 2.08 h)	50.1° 21:25	4.93	91%	96.5°
2040-05-29 Tue	57	—	unknown	22:55–01:05 (good, 2.17 h)	50.1° 21:20	4.89	84%	111.3°
2040-05-30 Wed	56	—	unknown	22:55–01:10 (good, 2.25 h)	50.1° 21:15	4.85	74%	125.9°
2040-05-31 Thu	55	—	unknown	22:55–01:05 (good, 2.17 h)	50.1° 21:15	4.81	63%	140.1°
2040-06-01 Fri	52	—	unknown	23:00–01:00 (good, 2.0 h)	50.1° 21:10	4.77	52%	154.1°
2040-06-02 Sat	51	—	unknown	23:00–00:55 (good, 1.92 h)	50.1° 21:05	4.74	41%	167.7°
2040-06-03 Sun	49	—	unknown	23:00–00:55 (good, 1.92 h)	50.1° 21:00	4.71	31%	179.0°
2040-06-04 Mon	47	—	unknown	23:00–00:50 (good, 1.83 h)	50.1° 20:55	4.67	21%	166.0°
2040-06-05 Tue	45	—	unknown	23:05–00:45 (good, 1.67 h)	50.1° 20:55	4.64	14%	153.2°
2040-06-06 Wed	43	—	unknown	23:05–00:40 (good, 1.58 h)	50.1° 20:50	4.62	8%	140.7°
2040-06-07 Thu	41	—	unknown	23:05–00:35 (good, 1.5 h)	50.1° 20:45	4.59	3%	128.3°
2040-06-08 Fri	40	—	unknown	23:05–00:35 (good, 1.5 h)	50.1° 20:40	4.57	1%	116.1°
2040-06-09 Sat	38	—	unknown	23:05–00:30 (good, 1.42 h)	50.1° 20:35	4.54	0%	104.0°
2040-06-10 Sun	36	—	unknown	23:10–00:25 (good, 1.25 h)	50.1° 20:35	4.52	1%	92.1°
2040-06-11 Mon	35	—	unknown	23:10–00:20 (good, 1.17 h)	50.1° 20:30	4.5	4%	80.2°
2040-06-12 Tue	32	—	unknown	23:10–00:15 (good, 1.08 h)	50.1° 20:25	4.49	9%	68.4°
2040-06-13 Wed	29	—	unknown	23:10–00:15 (good, 1.08 h)	50.1° 20:20	4.47	15%	56.6°
2040-06-14 Thu	25	—	unknown	23:10–00:00 (good, 0.83 h)	50.1° 20:20	4.46	22%	44.7°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2040-05-16&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.