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: 05-24 (68), 05-25 (67), 05-23 (66), 05-26 (66), 05-27 (64) — by astronomy; check the weather when the night is within four days.

2027-05-12astronomy score per night — click a bar for that night2027-06-10

night of	astronomy	weather	overall	best window	highest	dark h	Moon	Moon sep.
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°
2027-05-18 Tue	18	—	unknown	22:35–01:55 (marginal, 3.33 h)	50.2° 22:05	5.43	97%	35.1°
2027-05-19 Wed	24	—	unknown	22:40–02:00 (marginal, 3.33 h)	50.2° 22:05	5.38	100%	47.6°
2027-05-20 Thu	32	—	unknown	22:40–22:50 (good, 0.17 h)	50.2° 22:00	5.33	100%	60.0°
2027-05-21 Fri	41	—	unknown	22:40–00:20 (good, 1.67 h)	50.2° 21:55	5.28	98%	72.2°
2027-05-22 Sat	62	—	unknown	22:45–01:15 (good, 2.5 h)	50.2° 21:50	5.23	94%	84.2°
2027-05-23 Sun	66	—	unknown	22:45–01:20 (good, 2.58 h)	50.2° 21:45	5.19	89%	96.1°
2027-05-24 Mon	68	—	unknown	22:45–01:25 (good, 2.67 h)	50.2° 21:45	5.14	82%	107.9°
2027-05-25 Tue	67	—	unknown	22:50–01:25 (good, 2.58 h)	50.2° 21:40	5.09	74%	119.6°
2027-05-26 Wed	66	—	unknown	22:50–01:25 (good, 2.58 h)	50.2° 21:35	5.05	66%	131.2°
2027-05-27 Thu	64	—	unknown	22:50–01:25 (good, 2.58 h)	50.2° 21:30	5.0	56%	142.9°
2027-05-28 Fri	63	—	unknown	22:50–01:20 (good, 2.5 h)	50.2° 21:25	4.96	47%	154.4°
2027-05-29 Sat	60	—	unknown	22:55–01:15 (good, 2.33 h)	50.2° 21:25	4.92	37%	165.3°
2027-05-30 Sun	58	—	unknown	22:55–01:10 (good, 2.25 h)	50.2° 21:20	4.88	27%	171.2°
2027-05-31 Mon	56	—	unknown	22:55–01:10 (good, 2.25 h)	50.2° 21:15	4.84	19%	163.7°
2027-06-01 Tue	55	—	unknown	22:55–01:05 (good, 2.17 h)	50.2° 21:10	4.8	11%	151.5°
2027-06-02 Wed	52	—	unknown	23:00–01:00 (good, 2.0 h)	50.2° 21:10	4.77	5%	138.1°
2027-06-03 Thu	50	—	unknown	23:00–00:55 (good, 1.92 h)	50.2° 21:05	4.73	1%	124.2°
2027-06-04 Fri	49	—	unknown	23:00–00:50 (good, 1.83 h)	50.2° 21:00	4.7	0%	109.8°
2027-06-05 Sat	47	—	unknown	23:00–00:50 (good, 1.83 h)	50.2° 20:55	4.67	2%	95.2°
2027-06-06 Sun	44	—	unknown	23:05–00:45 (good, 1.67 h)	50.2° 20:50	4.64	6%	80.4°
2027-06-07 Mon	40	—	unknown	23:05–00:40 (good, 1.58 h)	50.2° 20:50	4.61	14%	65.8°
2027-06-08 Tue	35	—	unknown	23:05–00:35 (good, 1.5 h)	50.2° 20:45	4.59	23%	51.4°
2027-06-09 Wed	28	—	unknown	23:05–00:20 (good, 1.25 h)	50.2° 20:40	4.56	33%	37.4°
2027-06-10 Thu	22	—	unknown	23:05–00:05 (good, 1.0 h)	50.2° 20:35	4.54	44%	24.0°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2027-05-12&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.