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: 04-09 (93), 04-10 (93), 04-11 (93), 04-12 (93), 04-13 (93) — by astronomy; check the weather when the night is within four days.

2042-04-09astronomy score per night — click a bar for that night2042-05-08

night of	astronomy	weather	overall	best window	highest	dark h	Moon	Moon sep.
2042-04-09 Wed	93	—	unknown	21:35–02:55 (good, 5.33 h)	50.1° 00:40	7.63	83%	62.8°
2042-04-10 Thu	93	—	unknown	21:35–04:00 (good, 6.42 h)	50.1° 00:35	7.57	75%	75.3°
2042-04-11 Fri	93	—	unknown	21:40–04:05 (good, 6.42 h)	50.1° 00:30	7.52	66%	88.0°
2042-04-12 Sat	93	—	unknown	21:40–04:10 (good, 6.5 h)	50.1° 00:25	7.46	56%	101.0°
2042-04-13 Sun	93	—	unknown	21:40–04:10 (good, 6.5 h)	50.1° 00:25	7.4	45%	114.4°
2042-04-14 Mon	93	—	unknown	21:45–04:10 (good, 6.42 h)	50.1° 00:20	7.34	34%	128.1°
2042-04-15 Tue	93	—	unknown	21:45–04:05 (good, 6.33 h)	50.1° 00:15	7.29	24%	142.3°
2042-04-16 Wed	93	—	unknown	21:45–04:05 (good, 6.33 h)	50.1° 00:10	7.23	14%	156.8°
2042-04-17 Thu	93	—	unknown	21:50–04:00 (good, 6.17 h)	50.1° 00:10	7.17	7%	171.4°
2042-04-18 Fri	93	—	unknown	21:50–03:55 (good, 6.08 h)	50.1° 00:05	7.11	2%	172.5°
2042-04-19 Sat	93	—	unknown	21:50–03:50 (good, 6.0 h)	50.1° 00:00	7.05	0%	157.7°
2042-04-20 Sun	93	—	unknown	21:50–03:50 (good, 6.0 h)	50.1° 23:55	7.0	1%	142.8°
2042-04-21 Mon	93	—	unknown	21:55–03:45 (good, 5.83 h)	50.1° 23:50	6.94	5%	128.0°
2042-04-22 Tue	93	—	unknown	21:55–03:40 (good, 5.75 h)	50.1° 23:50	6.88	11%	113.7°
2042-04-23 Wed	92	—	unknown	21:55–03:35 (good, 5.67 h)	50.1° 23:45	6.82	19%	99.8°
2042-04-24 Thu	88	—	unknown	22:00–03:30 (good, 5.5 h)	50.1° 23:40	6.76	28%	86.3°
2042-04-25 Fri	83	—	unknown	22:00–03:30 (good, 5.5 h)	50.1° 23:35	6.71	38%	73.3°
2042-04-26 Sat	73	—	unknown	22:00–03:25 (good, 5.42 h)	50.1° 23:30	6.65	48%	60.7°
2042-04-27 Sun	60	—	unknown	22:40–02:55 (good, 4.25 h)	50.1° 23:30	6.59	58%	48.5°
2042-04-28 Mon	42	—	unknown	22:05–03:45 (marginal, 5.67 h)	50.1° 23:25	6.53	68%	36.4°
2042-04-29 Tue	31	—	unknown	22:05–03:30 (marginal, 5.42 h)	50.1° 23:20	6.47	76%	24.5°
2042-04-30 Wed	24	—	unknown	22:10–03:20 (marginal, 5.17 h)	50.1° 23:15	6.41	84%	12.9°
2042-05-01 Thu	20	—	unknown	22:10–03:05 (marginal, 4.92 h)	50.1° 23:15	6.36	90%	3.0°
2042-05-02 Fri	17	—	unknown	22:10–02:55 (marginal, 4.75 h)	50.1° 23:10	6.3	95%	11.5°
2042-05-03 Sat	18	—	unknown	22:15–02:40 (marginal, 4.42 h)	50.1° 23:05	6.24	98%	23.2°
2042-05-04 Sun	23	—	unknown	22:15–02:40 (marginal, 4.42 h)	50.1° 23:00	6.18	100%	35.2°
2042-05-05 Mon	35	—	unknown	22:15–02:50 (marginal, 4.58 h)	50.1° 22:55	6.13	100%	47.4°
2042-05-06 Tue	49	—	unknown	22:20–23:45 (good, 1.42 h)	50.1° 22:55	6.07	97%	59.7°
2042-05-07 Wed	83	—	unknown	22:20–01:25 (good, 3.08 h)	50.1° 22:50	6.01	93%	72.2°
2042-05-08 Thu	91	—	unknown	22:20–02:10 (good, 3.83 h)	50.1° 22:45	5.96	87%	85.0°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2042-04-09&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.