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: 04-13 (93), 04-14 (93), 04-15 (93), 04-29 (93), 04-30 (93) — by astronomy; check the weather when the night is within four days.

2040-04-13astronomy score per night — click a bar for that night2040-05-12

night of	astronomy	weather	overall	best window	highest	dark h	Moon	Moon sep.
2040-04-13 Fri	93	—	unknown	21:40–04:15 (good, 6.58 h)	50.1° 00:20	7.37	6%	133.4°
2040-04-14 Sat	93	—	unknown	21:45–04:10 (good, 6.42 h)	50.1° 00:20	7.32	11%	121.0°
2040-04-15 Sun	93	—	unknown	21:45–04:05 (good, 6.33 h)	50.1° 00:15	7.26	18%	108.8°
2040-04-16 Mon	92	—	unknown	21:45–04:00 (good, 6.25 h)	50.1° 00:10	7.2	26%	96.8°
2040-04-17 Tue	88	—	unknown	21:50–04:00 (good, 6.17 h)	50.1° 00:05	7.14	35%	84.9°
2040-04-18 Wed	83	—	unknown	21:50–03:55 (good, 6.08 h)	50.1° 00:00	7.08	44%	73.1°
2040-04-19 Thu	72	—	unknown	21:50–03:50 (good, 6.0 h)	50.1° 00:00	7.03	54%	61.2°
2040-04-20 Fri	61	—	unknown	23:50–03:20 (good, 3.5 h)	50.1° 23:55	6.97	63%	49.2°
2040-04-21 Sat	42	—	unknown	21:55–04:05 (marginal, 6.17 h)	50.1° 23:50	6.91	72%	37.0°
2040-04-22 Sun	29	—	unknown	21:55–03:55 (marginal, 6.0 h)	50.1° 23:45	6.85	81%	24.5°
2040-04-23 Mon	22	—	unknown	22:00–03:40 (marginal, 5.67 h)	50.1° 23:40	6.79	88%	11.7°
2040-04-24 Tue	18	—	unknown	22:00–03:25 (marginal, 5.42 h)	50.1° 23:40	6.74	94%	1.6°
2040-04-25 Wed	17	—	unknown	22:00–03:05 (marginal, 5.08 h)	50.1° 23:35	6.68	98%	15.1°
2040-04-26 Thu	21	—	unknown	22:00–03:00 (marginal, 5.0 h)	50.1° 23:30	6.62	100%	29.1°
2040-04-27 Fri	35	—	unknown	22:05–03:15 (marginal, 5.17 h)	50.1° 23:25	6.56	99%	43.3°
2040-04-28 Sat	78	—	unknown	22:05–23:50 (good, 1.75 h)	50.1° 23:25	6.5	96%	57.7°
2040-04-29 Sun	93	—	unknown	22:05–01:55 (good, 3.83 h)	50.1° 23:20	6.44	90%	72.2°
2040-04-30 Mon	93	—	unknown	22:10–02:45 (good, 4.58 h)	50.1° 23:15	6.39	81%	86.8°
2040-05-01 Tue	93	—	unknown	22:10–02:50 (good, 4.67 h)	50.1° 23:10	6.33	71%	101.2°
2040-05-02 Wed	93	—	unknown	22:10–02:55 (good, 4.75 h)	50.1° 23:05	6.27	60%	115.5°
2040-05-03 Thu	93	—	unknown	22:15–02:55 (good, 4.67 h)	50.1° 23:05	6.21	49%	129.6°
2040-05-04 Fri	93	—	unknown	22:15–02:50 (good, 4.58 h)	50.1° 23:00	6.16	38%	143.5°
2040-05-05 Sat	93	—	unknown	22:15–02:45 (good, 4.5 h)	50.1° 22:55	6.1	27%	157.2°
2040-05-06 Sun	93	—	unknown	22:20–02:45 (good, 4.42 h)	50.1° 22:50	6.04	18%	170.7°
2040-05-07 Mon	93	—	unknown	22:20–02:40 (good, 4.33 h)	50.1° 22:45	5.98	11%	176.0°
2040-05-08 Tue	93	—	unknown	22:20–02:35 (good, 4.25 h)	50.1° 22:45	5.93	5%	162.9°
2040-05-09 Wed	93	—	unknown	22:25–02:30 (good, 4.08 h)	50.1° 22:40	5.87	2%	150.1°
2040-05-10 Thu	93	—	unknown	22:25–02:25 (good, 4.0 h)	50.1° 22:35	5.82	0%	137.4°
2040-05-11 Fri	93	—	unknown	22:25–02:25 (good, 4.0 h)	50.1° 22:30	5.76	1%	125.0°
2040-05-12 Sat	92	—	unknown	22:30–02:20 (good, 3.83 h)	50.1° 22:25	5.71	3%	112.8°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2040-04-13&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.