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: 12-19 (89), 12-20 (89), 12-21 (89), 12-22 (89), 12-23 (89) — by astronomy; check the weather when the night is within four days.

2038-12-13astronomy score per night — click a bar for that night2039-01-11

night of	astronomy	weather	overall	best window	highest	dark h	Moon	Moon sep.
2038-12-13 Mon	19	—	unknown	21:20–00:05 (marginal, 2.75 h)	42.9° 00:25	11.48	96%	37.6°
2038-12-14 Tue	31	—	unknown	20:50–03:20 (marginal, 6.5 h)	42.9° 00:25	11.49	90%	46.5°
2038-12-15 Wed	48	—	unknown	20:35–03:40 (marginal, 7.08 h)	42.9° 00:20	11.49	84%	56.7°
2038-12-16 Thu	76	—	unknown	21:00–00:55 (good, 3.92 h)	42.9° 00:15	11.5	75%	67.6°
2038-12-17 Fri	85	—	unknown	21:00–02:55 (good, 5.92 h)	42.9° 00:10	11.5	66%	79.1°
2038-12-18 Sat	88	—	unknown	20:55–03:10 (good, 6.25 h)	42.9° 00:10	11.5	55%	90.9°
2038-12-19 Sun	89	—	unknown	20:50–03:15 (good, 6.42 h)	42.9° 00:05	11.51	44%	103.0°
2038-12-20 Mon	89	—	unknown	20:45–03:15 (good, 6.5 h)	42.9° 00:00	11.51	33%	115.2°
2038-12-21 Tue	89	—	unknown	20:40–03:15 (good, 6.58 h)	42.9° 23:55	11.51	23%	127.3°
2038-12-22 Wed	89	—	unknown	20:40–03:10 (good, 6.5 h)	42.9° 23:50	11.51	14%	138.5°
2038-12-23 Thu	89	—	unknown	20:35–03:05 (good, 6.5 h)	42.9° 23:50	11.51	6%	147.6°
2038-12-24 Fri	89	—	unknown	20:30–03:05 (good, 6.58 h)	42.9° 23:45	11.5	2%	152.1°
2038-12-25 Sat	89	—	unknown	20:25–03:00 (good, 6.58 h)	42.9° 23:40	11.5	0%	149.7°
2038-12-26 Sun	89	—	unknown	20:20–02:55 (good, 6.58 h)	42.9° 23:35	11.5	1%	141.9°
2038-12-27 Mon	89	—	unknown	20:20–02:50 (good, 6.5 h)	42.9° 23:30	11.49	5%	131.5°
2038-12-28 Tue	89	—	unknown	20:15–02:50 (good, 6.58 h)	42.9° 23:30	11.48	11%	120.2°
2038-12-29 Wed	89	—	unknown	20:15–02:45 (good, 6.5 h)	42.9° 23:25	11.48	18%	108.6°
2038-12-30 Thu	89	—	unknown	20:10–02:40 (good, 6.5 h)	42.9° 23:20	11.47	27%	97.1°
2038-12-31 Fri	89	—	unknown	20:15–02:35 (good, 6.33 h)	42.9° 23:15	11.46	37%	86.0°
2039-01-01 Sat	88	—	unknown	20:20–02:30 (good, 6.17 h)	42.9° 23:15	11.45	46%	75.1°
2039-01-02 Sun	84	—	unknown	20:40–02:30 (good, 5.83 h)	42.9° 23:10	11.44	56%	64.7°
2039-01-03 Mon	73	—	unknown	22:40–02:25 (good, 3.75 h)	42.9° 23:05	11.43	65%	54.7°
2039-01-04 Tue	49	—	unknown	19:40–02:50 (marginal, 7.17 h)	42.9° 23:00	11.42	74%	45.3°
2039-01-05 Wed	32	—	unknown	20:00–02:35 (marginal, 6.58 h)	42.9° 22:55	11.4	82%	37.0°
2039-01-06 Thu	20	—	unknown	22:50–02:05 (marginal, 3.25 h)	42.9° 22:55	11.39	88%	30.7°
2039-01-07 Fri	13	—	unknown	—	42.9° 22:50	11.38	94%	27.8°
2039-01-08 Sat	10	—	unknown	—	42.9° 22:45	11.36	98%	29.6°
2039-01-09 Sun	14	—	unknown	19:55–20:25 (marginal, 0.5 h)	42.9° 22:40	11.34	100%	35.5°
2039-01-10 Mon	22	—	unknown	19:20–23:15 (marginal, 3.92 h)	42.9° 22:35	11.33	100%	44.0°
2039-01-11 Tue	35	—	unknown	18:55–01:30 (marginal, 6.58 h)	42.9° 22:35	11.31	98%	54.0°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2038-12-13&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.