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: 01-17 (93), 01-18 (93), 01-31 (93), 02-01 (93), 02-02 (93) — by astronomy; check the weather when the night is within four days.

2027-01-17astronomy score per night — click a bar for that night2027-02-15

night of	astronomy	weather	overall	best window	highest	dark h	Moon	Moon sep.
2027-01-17 Sun	93	—	unknown	01:25–06:10 (good, 4.75 h)	50.2° 05:00	11.19	72%	130.9°
2027-01-18 Mon	93	—	unknown	01:25–06:10 (good, 4.75 h)	50.2° 05:00	11.16	82%	116.8°
2027-01-19 Tue	92	—	unknown	01:30–06:10 (good, 4.67 h)	50.2° 04:55	11.14	90%	102.2°
2027-01-20 Wed	65	—	unknown	02:50–06:10 (good, 3.33 h)	50.2° 04:50	11.11	96%	87.3°
2027-01-21 Thu	47	—	unknown	05:10–06:05 (good, 0.92 h)	50.2° 04:45	11.09	100%	72.2°
2027-01-22 Fri	32	—	unknown	01:10–06:05 (marginal, 4.92 h)	50.2° 04:45	11.06	100%	57.2°
2027-01-23 Sat	22	—	unknown	02:05–06:05 (marginal, 4.0 h)	50.2° 04:40	11.04	97%	42.4°
2027-01-24 Sun	19	—	unknown	02:50–06:05 (marginal, 3.25 h)	50.2° 04:35	11.01	92%	28.2°
2027-01-25 Mon	24	—	unknown	00:50–06:05 (marginal, 5.25 h)	50.2° 04:30	10.98	84%	15.2°
2027-01-26 Tue	33	—	unknown	00:25–06:05 (marginal, 5.67 h)	50.2° 04:25	10.95	75%	8.6°
2027-01-27 Wed	47	—	unknown	00:10–06:05 (marginal, 5.92 h)	50.2° 04:25	10.92	65%	16.8°
2027-01-28 Thu	73	—	unknown	00:30–06:05 (good, 5.58 h)	50.2° 04:20	10.89	55%	28.6°
2027-01-29 Fri	87	—	unknown	00:30–06:00 (good, 5.5 h)	50.2° 04:15	10.86	45%	40.7°
2027-01-30 Sat	92	—	unknown	00:25–06:00 (good, 5.58 h)	50.2° 04:10	10.83	36%	52.7°
2027-01-31 Sun	93	—	unknown	00:20–06:00 (good, 5.67 h)	50.2° 04:05	10.8	27%	64.5°
2027-02-01 Mon	93	—	unknown	00:15–06:00 (good, 5.75 h)	50.2° 04:05	10.77	19%	76.2°
2027-02-02 Tue	93	—	unknown	00:10–06:00 (good, 5.83 h)	50.2° 04:00	10.73	12%	87.9°
2027-02-03 Wed	93	—	unknown	00:10–06:00 (good, 5.83 h)	50.2° 03:55	10.7	7%	99.6°
2027-02-04 Thu	93	—	unknown	00:05–05:55 (good, 5.83 h)	50.2° 03:50	10.66	3%	111.3°
2027-02-05 Fri	93	—	unknown	00:00–05:55 (good, 5.92 h)	50.2° 03:50	10.63	0%	123.1°
2027-02-06 Sat	93	—	unknown	23:55–05:55 (good, 6.0 h)	50.2° 03:45	10.59	0%	134.9°
2027-02-07 Sun	93	—	unknown	23:55–05:55 (good, 6.0 h)	50.2° 03:40	10.56	2%	146.7°
2027-02-08 Mon	93	—	unknown	23:50–05:55 (good, 6.08 h)	50.2° 03:35	10.52	5%	158.3°
2027-02-09 Tue	93	—	unknown	23:45–05:50 (good, 6.08 h)	50.2° 03:30	10.49	10%	168.6°
2027-02-10 Wed	93	—	unknown	23:40–05:50 (good, 6.17 h)	50.2° 03:30	10.45	17%	170.1°
2027-02-11 Thu	93	—	unknown	23:35–05:50 (good, 6.25 h)	50.2° 03:25	10.41	25%	160.1°
2027-02-12 Fri	93	—	unknown	23:35–05:50 (good, 6.25 h)	50.2° 03:20	10.37	35%	147.8°
2027-02-13 Sat	93	—	unknown	23:35–05:45 (good, 6.17 h)	50.2° 03:15	10.33	46%	134.8°
2027-02-14 Sun	93	—	unknown	23:30–05:45 (good, 6.25 h)	50.2° 03:10	10.3	57%	121.3°
2027-02-15 Mon	93	—	unknown	23:35–05:45 (good, 6.17 h)	50.2° 03:10	10.26	68%	107.4°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2027-01-17&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.