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: 03-29 (17), 03-30 (15), 03-31 (13), 04-01 (12), 04-02 (10) — by astronomy; check the weather when the night is within four days.

2027-03-29astronomy score per night — click a bar for that night2027-04-27

night of	astronomy	weather	overall	best window	highest	dark h	Moon	Moon sep.
2027-03-29 Mon	17	—	unknown	21:20–21:50 (good, 0.5 h)	42.9° 18:30	8.26	51%	144.9°
2027-03-30 Tue	15	—	unknown	21:20–21:45 (good, 0.42 h)	42.9° 18:25	8.2	42%	139.6°
2027-03-31 Wed	13	—	unknown	21:25–21:40 (good, 0.25 h)	42.9° 18:25	8.15	32%	132.3°
2027-04-01 Thu	12	—	unknown	21:25–21:40 (good, 0.25 h)	42.9° 18:20	8.1	24%	123.7°
2027-04-02 Fri	10	—	unknown	21:25–21:35 (good, 0.17 h)	42.9° 18:15	8.04	16%	114.2°
2027-04-03 Sat	9	—	unknown	21:25–21:30 (good, 0.08 h)	42.9° 18:10	7.99	10%	104.2°
2027-04-04 Sun	7	—	unknown	21:30–21:55 (marginal, 0.42 h)	42.9° 18:05	7.93	5%	93.7°
2027-04-05 Mon	6	—	unknown	21:30–21:55 (marginal, 0.42 h)	42.9° 18:05	7.87	1%	83.0°
2027-04-06 Tue	5	—	unknown	21:30–21:50 (marginal, 0.33 h)	42.9° 18:00	7.82	0%	72.1°
2027-04-07 Wed	4	—	unknown	21:30–21:45 (marginal, 0.25 h)	42.9° 17:55	7.76	1%	61.3°
2027-04-08 Thu	3	—	unknown	21:00–21:10 (marginal, 0.17 h)	42.9° 17:50	7.71	5%	51.0°
2027-04-09 Fri	2	—	unknown	—	42.9° 17:45	7.65	10%	41.9°
2027-04-10 Sat	1	—	unknown	—	42.9° 17:45	7.59	18%	35.3°
2027-04-11 Sun	1	—	unknown	—	42.9° 17:40	7.54	28%	32.8°
2027-04-12 Mon	0	—	unknown	—	42.9° 17:35	7.48	38%	35.5°
2027-04-13 Tue	0	—	unknown	—	42.9° 17:30	7.42	50%	42.4°
2027-04-14 Wed	0	—	unknown	—	42.9° 17:30	7.36	61%	51.9°
2027-04-15 Thu	0	—	unknown	—	42.9° 17:25	7.31	72%	62.7°
2027-04-16 Fri	0	—	unknown	—	42.9° 17:20	7.25	81%	74.1°
2027-04-17 Sat	0	—	unknown	—	42.9° 17:15	7.19	89%	85.8°
2027-04-18 Sun	0	—	unknown	—	42.9° 17:10	7.13	95%	97.4°
2027-04-19 Mon	0	—	unknown	—	42.9° 17:10	7.08	99%	108.7°
2027-04-20 Tue	0	—	unknown	—	42.9° 17:05	7.02	100%	119.5°
2027-04-21 Wed	0	—	unknown	—	42.9° 17:00	6.96	99%	129.4°
2027-04-22 Thu	0	—	unknown	—	42.9° 16:55	6.9	96%	137.9°
2027-04-23 Fri	0	—	unknown	—	42.9° 16:50	6.84	90%	144.1°
2027-04-24 Sat	0	—	unknown	—	42.9° 16:50	6.78	84%	147.1°
2027-04-25 Sun	0	—	unknown	—	42.9° 16:45	6.73	76%	146.2°
2027-04-26 Mon	0	—	unknown	—	42.9° 16:40	6.67	68%	141.9°
2027-04-27 Tue	0	—	unknown	—	42.9° 16:35	6.61	59%	135.1°

Download: CSV · JSON

💡 API

curl -sS "https://devops.majbase.com/rozhen-planner/calendar-api?target=M31&date=2027-03-29&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.