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: 05-13 (92), 05-14 (91), 05-15 (89), 05-16 (86), 05-17 (85) — by astronomy; check the weather when the night is within four days.

2039-05-13astronomy score per night — click a bar for that night2039-06-11

night of	astronomy	weather	overall	best window	highest	dark h	Moon	Moon sep.
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°
2039-05-26 Thu	63	—	unknown	22:50–01:25 (good, 2.58 h)	50.1° 21:35	5.04	13%	78.2°
2039-05-27 Fri	57	—	unknown	22:50–01:25 (good, 2.58 h)	50.1° 21:30	5.0	20%	66.1°
2039-05-28 Sat	49	—	unknown	22:50–01:10 (good, 2.33 h)	50.1° 21:30	4.96	28%	53.8°
2039-05-29 Sun	39	—	unknown	22:55–01:00 (good, 2.08 h)	50.1° 21:25	4.92	38%	41.3°
2039-05-30 Mon	29	—	unknown	22:55–00:40 (good, 1.75 h)	50.1° 21:20	4.88	48%	28.5°
2039-05-31 Tue	22	—	unknown	22:55–01:35 (marginal, 2.67 h)	50.1° 21:15	4.84	59%	15.3°
2039-06-01 Wed	16	—	unknown	22:55–01:20 (marginal, 2.42 h)	50.1° 21:10	4.8	69%	1.6°
2039-06-02 Thu	12	—	unknown	23:00–01:05 (marginal, 2.08 h)	50.1° 21:10	4.77	79%	12.5°
2039-06-03 Fri	9	—	unknown	23:00–00:50 (marginal, 1.83 h)	50.1° 21:05	4.73	88%	27.0°
2039-06-04 Sat	11	—	unknown	23:00–00:50 (marginal, 1.83 h)	50.1° 21:00	4.7	95%	41.9°
2039-06-05 Sun	15	—	unknown	23:00–00:55 (marginal, 1.92 h)	50.1° 20:55	4.67	99%	57.1°
2039-06-06 Mon	20	—	unknown	23:05–01:05 (marginal, 2.0 h)	50.1° 20:50	4.64	100%	72.3°
2039-06-07 Tue	26	—	unknown	23:05–00:10 (good, 1.08 h)	50.1° 20:50	4.61	98%	87.5°
2039-06-08 Wed	37	—	unknown	23:05–00:20 (good, 1.25 h)	50.1° 20:45	4.58	93%	102.5°
2039-06-09 Thu	39	—	unknown	23:05–00:25 (good, 1.33 h)	50.1° 20:40	4.56	86%	117.0°
2039-06-10 Fri	38	—	unknown	23:05–00:30 (good, 1.42 h)	50.1° 20:35	4.54	77%	131.2°
2039-06-11 Sat	35	—	unknown	23:10–00:25 (good, 1.25 h)	50.1° 20:30	4.52	67%	144.8°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2039-05-13&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.