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: 04-23 (93), 04-24 (93), 04-25 (93), 04-26 (93), 04-27 (93) — by astronomy; check the weather when the night is within four days.

2027-04-18astronomy score per night — click a bar for that night2027-05-17

night of	astronomy	weather	overall	best window	highest	dark h	Moon	Moon sep.
2027-04-18 Sun	23	—	unknown	21:50–04:00 (marginal, 6.17 h)	50.2° 00:05	7.13	95%	8.7°
2027-04-19 Mon	22	—	unknown	21:50–03:45 (marginal, 5.92 h)	50.2° 00:00	7.08	99%	14.4°
2027-04-20 Tue	26	—	unknown	21:50–03:40 (marginal, 5.83 h)	50.2° 23:55	7.02	100%	26.4°
2027-04-21 Wed	39	—	unknown	21:55–03:45 (marginal, 5.83 h)	50.2° 23:55	6.96	99%	39.1°
2027-04-22 Thu	85	—	unknown	21:55–23:30 (good, 1.58 h)	50.2° 23:50	6.9	96%	51.6°
2027-04-23 Fri	93	—	unknown	21:55–01:45 (good, 3.83 h)	50.2° 23:45	6.84	90%	64.0°
2027-04-24 Sat	93	—	unknown	22:00–03:00 (good, 5.0 h)	50.2° 23:40	6.78	84%	76.2°
2027-04-25 Sun	93	—	unknown	22:00–03:10 (good, 5.17 h)	50.2° 23:35	6.73	76%	88.2°
2027-04-26 Mon	93	—	unknown	22:00–03:15 (good, 5.25 h)	50.2° 23:35	6.67	68%	100.0°
2027-04-27 Tue	93	—	unknown	22:05–03:15 (good, 5.17 h)	50.2° 23:30	6.61	59%	111.7°
2027-04-28 Wed	93	—	unknown	22:05–03:15 (good, 5.17 h)	50.2° 23:25	6.55	49%	123.4°
2027-04-29 Thu	93	—	unknown	22:05–03:15 (good, 5.17 h)	50.2° 23:20	6.49	40%	135.1°
2027-04-30 Fri	93	—	unknown	22:05–03:10 (good, 5.08 h)	50.2° 23:15	6.43	31%	146.8°
2027-05-01 Sat	93	—	unknown	22:10–03:05 (good, 4.92 h)	50.2° 23:15	6.38	22%	158.5°
2027-05-02 Sun	93	—	unknown	22:10–03:00 (good, 4.83 h)	50.2° 23:10	6.32	14%	168.8°
2027-05-03 Mon	93	—	unknown	22:10–03:00 (good, 4.83 h)	50.2° 23:05	6.26	8%	169.7°
2027-05-04 Tue	93	—	unknown	22:15–02:55 (good, 4.67 h)	50.2° 23:00	6.2	3%	159.1°
2027-05-05 Wed	93	—	unknown	22:15–02:50 (good, 4.58 h)	50.2° 23:00	6.15	0%	146.2°
2027-05-06 Thu	93	—	unknown	22:15–02:45 (good, 4.5 h)	50.2° 22:55	6.09	0%	132.6°
2027-05-07 Fri	93	—	unknown	22:20–02:40 (good, 4.33 h)	50.2° 22:50	6.03	3%	118.5°
2027-05-08 Sat	93	—	unknown	22:20–02:40 (good, 4.33 h)	50.2° 22:45	5.98	8%	104.3°
2027-05-09 Sun	90	—	unknown	22:20–02:35 (good, 4.25 h)	50.2° 22:40	5.92	16%	90.0°
2027-05-10 Mon	86	—	unknown	22:25–02:30 (good, 4.08 h)	50.2° 22:40	5.86	25%	75.7°
2027-05-11 Tue	75	—	unknown	22:25–02:25 (good, 4.0 h)	50.2° 22:35	5.81	36%	61.6°
2027-05-12 Wed	57	—	unknown	22:25–02:05 (good, 3.67 h)	50.2° 22:30	5.75	47%	47.6°
2027-05-13 Thu	40	—	unknown	22:30–02:45 (marginal, 4.25 h)	50.2° 22:25	5.7	58%	34.0°
2027-05-14 Fri	30	—	unknown	22:30–02:40 (marginal, 4.17 h)	50.2° 22:20	5.64	69%	21.0°
2027-05-15 Sat	23	—	unknown	22:30–02:25 (marginal, 3.92 h)	50.2° 22:20	5.59	79%	10.3°
2027-05-16 Sun	18	—	unknown	22:35–02:15 (marginal, 3.67 h)	50.2° 22:15	5.54	87%	11.7°
2027-05-17 Mon	16	—	unknown	22:35–02:00 (marginal, 3.42 h)	50.2° 22:10	5.48	93%	22.8°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2027-04-18&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.