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 Great Orion Nebula: 12-25 (89), 12-26 (89), 12-27 (89), 12-28 (89), 12-29 (89) — by astronomy; check the weather when the night is within four days.

2040-12-19astronomy score per night — click a bar for that night2041-01-17

night of	astronomy	weather	overall	best window	highest	dark h	Moon	Moon sep.
2040-12-19 Wed	17	—	unknown	21:05–22:50 (marginal, 1.75 h)	42.9° 00:00	11.51	98%	38.6°
2040-12-20 Thu	27	—	unknown	20:30–02:25 (marginal, 5.92 h)	42.9° 00:00	11.51	94%	46.2°
2040-12-21 Fri	41	—	unknown	20:15–03:05 (marginal, 6.83 h)	42.9° 23:55	11.51	89%	55.1°
2040-12-22 Sat	59	—	unknown	21:30–22:05 (good, 0.58 h)	42.9° 23:50	11.51	83%	64.5°
2040-12-23 Sun	82	—	unknown	20:30–01:20 (good, 4.83 h)	42.9° 23:45	11.5	75%	74.4°
2040-12-24 Mon	87	—	unknown	20:30–02:30 (good, 6.0 h)	42.9° 23:40	11.5	67%	84.5°
2040-12-25 Tue	89	—	unknown	20:25–02:40 (good, 6.25 h)	42.9° 23:40	11.5	58%	94.8°
2040-12-26 Wed	89	—	unknown	20:20–02:45 (good, 6.42 h)	42.9° 23:35	11.49	48%	105.2°
2040-12-27 Thu	89	—	unknown	20:15–02:45 (good, 6.5 h)	42.9° 23:30	11.49	38%	115.6°
2040-12-28 Fri	89	—	unknown	20:10–02:45 (good, 6.58 h)	42.9° 23:25	11.48	28%	125.9°
2040-12-29 Sat	89	—	unknown	20:10–02:40 (good, 6.5 h)	42.9° 23:25	11.47	19%	135.7°
2040-12-30 Sun	89	—	unknown	20:05–02:40 (good, 6.58 h)	42.9° 23:20	11.47	11%	143.8°
2040-12-31 Mon	89	—	unknown	20:00–02:35 (good, 6.58 h)	42.9° 23:15	11.46	5%	148.5°
2041-01-01 Tue	89	—	unknown	19:55–02:30 (good, 6.58 h)	42.9° 23:10	11.45	1%	147.6°
2041-01-02 Wed	89	—	unknown	19:55–02:25 (good, 6.5 h)	42.9° 23:05	11.44	0%	141.2°
2041-01-03 Thu	89	—	unknown	19:50–02:20 (good, 6.5 h)	42.9° 23:05	11.42	2%	131.2°
2041-01-04 Fri	89	—	unknown	19:45–02:20 (good, 6.58 h)	42.9° 23:00	11.41	7%	119.6°
2041-01-05 Sat	89	—	unknown	19:45–02:15 (good, 6.5 h)	42.9° 22:55	11.4	14%	107.3°
2041-01-06 Sun	89	—	unknown	19:40–02:10 (good, 6.5 h)	42.9° 22:50	11.38	24%	94.8°
2041-01-07 Mon	89	—	unknown	19:45–02:05 (good, 6.33 h)	42.9° 22:45	11.37	34%	82.6°
2041-01-08 Tue	87	—	unknown	19:50–02:00 (good, 6.17 h)	42.9° 22:45	11.35	45%	70.9°
2041-01-09 Wed	81	—	unknown	20:35–02:00 (good, 5.42 h)	42.9° 22:40	11.34	56%	59.9°
2041-01-10 Thu	59	—	unknown	19:05–02:25 (marginal, 7.33 h)	42.9° 22:35	11.32	66%	49.8°
2041-01-11 Fri	40	—	unknown	19:20–02:15 (marginal, 6.92 h)	42.9° 22:30	11.3	75%	41.0°
2041-01-12 Sat	25	—	unknown	19:40–01:55 (marginal, 6.25 h)	42.9° 22:30	11.28	83%	34.5°
2041-01-13 Sun	16	—	unknown	00:20–01:15 (marginal, 0.92 h)	42.9° 22:25	11.26	90%	31.3°
2041-01-14 Mon	12	—	unknown	—	42.9° 22:20	11.24	95%	32.2°
2041-01-15 Tue	14	—	unknown	19:30–20:05 (marginal, 0.58 h)	42.9° 22:15	11.22	98%	36.9°
2041-01-16 Wed	20	—	unknown	18:55–22:35 (marginal, 3.67 h)	42.9° 22:10	11.2	100%	44.0°
2041-01-17 Thu	30	—	unknown	19:00–00:55 (marginal, 5.92 h)	42.9° 22:10	11.17	100%	52.6°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2040-12-19&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.