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: 05-20 (77), 05-19 (76), 05-21 (76), 05-18 (73), 05-22 (73) — by astronomy; check the weather when the night is within four days.

2041-05-18astronomy score per night — click a bar for that night2041-06-16

night of	astronomy	weather	overall	best window	highest	dark h	Moon	Moon sep.
2041-05-18 Sat	73	—	unknown	22:40–01:35 (good, 2.92 h)	50.1° 22:05	5.4	90%	89.7°
2041-05-19 Sun	76	—	unknown	22:40–01:40 (good, 3.0 h)	50.1° 22:00	5.35	82%	103.8°
2041-05-20 Mon	77	—	unknown	22:40–01:45 (good, 3.08 h)	50.1° 21:55	5.3	72%	118.0°
2041-05-21 Tue	76	—	unknown	22:40–01:45 (good, 3.08 h)	50.1° 21:55	5.25	62%	132.2°
2041-05-22 Wed	73	—	unknown	22:45–01:40 (good, 2.92 h)	50.1° 21:50	5.2	50%	146.3°
2041-05-23 Thu	71	—	unknown	22:45–01:35 (good, 2.83 h)	50.1° 21:45	5.16	39%	160.5°
2041-05-24 Fri	69	—	unknown	22:45–01:35 (good, 2.83 h)	50.1° 21:40	5.11	28%	174.4°
2041-05-25 Sat	66	—	unknown	22:50–01:30 (good, 2.67 h)	50.1° 21:35	5.07	18%	171.3°
2041-05-26 Sun	65	—	unknown	22:50–01:25 (good, 2.58 h)	50.1° 21:35	5.02	10%	157.5°
2041-05-27 Mon	63	—	unknown	22:50–01:20 (good, 2.5 h)	50.1° 21:30	4.98	5%	143.8°
2041-05-28 Tue	60	—	unknown	22:55–01:15 (good, 2.33 h)	50.1° 21:25	4.94	1%	130.2°
2041-05-29 Wed	58	—	unknown	22:55–01:15 (good, 2.33 h)	50.1° 21:20	4.9	0%	117.0°
2041-05-30 Thu	57	—	unknown	22:55–01:10 (good, 2.25 h)	50.1° 21:20	4.86	1%	104.0°
2041-05-31 Fri	56	—	unknown	22:55–01:05 (good, 2.17 h)	50.1° 21:15	4.82	4%	91.2°
2041-06-01 Sat	51	—	unknown	23:00–01:00 (good, 2.0 h)	50.1° 21:10	4.78	9%	78.8°
2041-06-02 Sun	47	—	unknown	23:00–01:00 (good, 2.0 h)	50.1° 21:05	4.75	16%	66.5°
2041-06-03 Mon	41	—	unknown	23:00–00:45 (good, 1.75 h)	50.1° 21:00	4.71	23%	54.5°
2041-06-04 Tue	34	—	unknown	23:00–00:35 (good, 1.58 h)	50.1° 21:00	4.68	32%	42.6°
2041-06-05 Wed	27	—	unknown	23:05–00:25 (good, 1.33 h)	50.1° 20:55	4.65	41%	30.8°
2041-06-06 Thu	21	—	unknown	23:05–01:10 (marginal, 2.08 h)	50.1° 20:50	4.62	50%	18.9°
2041-06-07 Fri	17	—	unknown	23:05–01:00 (marginal, 1.92 h)	50.1° 20:45	4.6	60%	7.1°
2041-06-08 Sat	13	—	unknown	23:05–00:50 (marginal, 1.75 h)	50.1° 20:40	4.57	69%	5.4°
2041-06-09 Sun	10	—	unknown	23:05–00:40 (marginal, 1.58 h)	50.1° 20:40	4.55	78%	17.7°
2041-06-10 Mon	8	—	unknown	23:05–00:25 (marginal, 1.33 h)	50.1° 20:35	4.53	86%	30.4°
2041-06-11 Tue	9	—	unknown	23:10–00:25 (marginal, 1.25 h)	50.1° 20:30	4.51	92%	43.5°
2041-06-12 Wed	11	—	unknown	23:10–00:30 (marginal, 1.33 h)	50.1° 20:25	4.49	97%	57.0°
2041-06-13 Thu	14	—	unknown	23:10–00:35 (marginal, 1.42 h)	50.1° 20:25	4.47	100%	70.8°
2041-06-14 Fri	17	—	unknown	23:10–23:40 (good, 0.5 h)	50.1° 20:20	4.46	100%	85.0°
2041-06-15 Sat	21	—	unknown	23:10–23:50 (good, 0.67 h)	50.1° 20:15	4.45	97%	99.4°
2041-06-16 Sun	26	—	unknown	23:10–23:55 (good, 0.75 h)	50.1° 20:10	4.44	92%	113.9°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2041-05-18&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.