{"assessment":{"best_window":{"end":"2026-12-21T04:05Z","end_local":"06:05","hours":2.42,"label":"good","mean_quality":0.85,"start":"2026-12-21T01:40Z","start_local":"03:40"},"cost":{"altitude":0.0,"clouds":0.0,"darkness":2.66,"moon":5.94},"formula":"astronomy = 100 * min(1, sky_hours / reference_hours) * peak_sky; overall = astronomy * score_weather / 100 (null when the weather is unknown)","hard_limit":null,"headline":"Astronomically worth it \u2014 weather unknown","hourly":[{"alt":null,"cloud":null,"high":null,"iso":"2026-12-20T15:00Z","label":"unusable","low":null,"mid":null,"moon_alt":36,"precip":null,"q":0.0,"rh":null,"sky":"civil twilight","temp":null,"time":"17:00","wind":null},{"alt":null,"cloud":null,"high":null,"iso":"2026-12-20T16:00Z","label":"poor","low":null,"mid":null,"moon_alt":47,"precip":null,"q":0.2,"rh":null,"sky":"astronomical twilight","temp":null,"time":"18:00","wind":null},{"alt":null,"cloud":null,"high":null,"iso":"2026-12-20T17:00Z","label":"marginal","low":null,"mid":null,"moon_alt":57,"precip":null,"q":0.37,"rh":null,"sky":"night","temp":null,"time":"19:00","wind":null},{"alt":null,"cloud":null,"high":null,"iso":"2026-12-20T18:00Z","label":"marginal","low":null,"mid":null,"moon_alt":65,"precip":null,"q":0.34,"rh":null,"sky":"night","temp":null,"time":"20:00","wind":null},{"alt":null,"cloud":null,"high":null,"iso":"2026-12-20T19:00Z","label":"marginal","low":null,"mid":null,"moon_alt":69,"precip":null,"q":0.34,"rh":null,"sky":"night","temp":null,"time":"21:00","wind":null},{"alt":null,"cloud":null,"high":null,"iso":"2026-12-20T20:00Z","label":"marginal","low":null,"mid":null,"moon_alt":65,"precip":null,"q":0.34,"rh":null,"sky":"night","temp":null,"time":"22:00","wind":null},{"alt":null,"cloud":null,"high":null,"iso":"2026-12-20T21:00Z","label":"marginal","low":null,"mid":null,"moon_alt":58,"precip":null,"q":0.37,"rh":null,"sky":"night","temp":null,"time":"23:00","wind":null},{"alt":null,"cloud":null,"high":null,"iso":"2026-12-20T22:00Z","label":"marginal","low":null,"mid":null,"moon_alt":48,"precip":null,"q":0.4,"rh":null,"sky":"night","temp":null,"time":"00:00","wind":null},{"alt":null,"cloud":null,"high":null,"iso":"2026-12-20T23:00Z","label":"marginal","low":null,"mid":null,"moon_alt":37,"precip":null,"q":0.45,"rh":null,"sky":"night","temp":null,"time":"01:00","wind":null},{"alt":null,"cloud":null,"high":null,"iso":"2026-12-21T00:00Z","label":"marginal","low":null,"mid":null,"moon_alt":26,"precip":null,"q":0.5,"rh":null,"sky":"night","temp":null,"time":"02:00","wind":null},{"alt":null,"cloud":null,"high":null,"iso":"2026-12-21T01:00Z","label":"marginal","low":null,"mid":null,"moon_alt":16,"precip":null,"q":0.56,"rh":null,"sky":"night","temp":null,"time":"03:00","wind":null},{"alt":null,"cloud":null,"high":null,"iso":"2026-12-21T02:00Z","label":"good","low":null,"mid":null,"moon_alt":6,"precip":null,"q":0.62,"rh":null,"sky":"night","temp":null,"time":"04:00","wind":null},{"alt":null,"cloud":null,"high":null,"iso":"2026-12-21T03:00Z","label":"good","low":null,"mid":null,"moon_alt":-4,"precip":null,"q":1.0,"rh":null,"sky":"night","temp":null,"time":"05:00","wind":null},{"alt":null,"cloud":null,"high":null,"iso":"2026-12-21T04:00Z","label":"good","low":null,"mid":null,"moon_alt":-12,"precip":null,"q":1.0,"rh":null,"sky":"night","temp":null,"time":"06:00","wind":null},{"alt":null,"cloud":null,"high":null,"iso":"2026-12-21T05:00Z","label":"poor","low":null,"mid":null,"moon_alt":-19,"precip":null,"q":0.15,"rh":null,"sky":"nautical twilight","temp":null,"time":"07:00","wind":null}],"peak_quality":1.0,"peak_sky":1.0,"quality_hours":6.32,"reasons":["moonlight cost 5.9 quality-hours","daylight and twilight cost 2.7 quality-hours"],"reference_hours":4.0,"score":null,"score_astronomy":100,"score_weather":null,"sky_hours":6.32,"verdict":"unknown","verdict_astronomy":"good","weather_known":false,"windows":[{"end":"2026-12-20T15:25Z","end_local":"17:25","hours":0.58,"label":"unusable","mean_quality":0.0,"start":"2026-12-20T14:50Z","start_local":"16:50"},{"end":"2026-12-20T16:35Z","end_local":"18:35","hours":1.17,"label":"poor","mean_quality":0.13,"start":"2026-12-20T15:25Z","start_local":"17:25"},{"end":"2026-12-21T01:40Z","end_local":"03:40","hours":9.08,"label":"marginal","mean_quality":0.41,"start":"2026-12-20T16:35Z","start_local":"18:35"},{"end":"2026-12-21T04:05Z","end_local":"06:05","hours":2.42,"label":"good","mean_quality":0.85,"start":"2026-12-21T01:40Z","start_local":"03:40"},{"end":"2026-12-21T04:40Z","end_local":"06:40","hours":0.58,"label":"marginal","mean_quality":0.5,"start":"2026-12-21T04:05Z","start_local":"06:05"},{"end":"2026-12-21T05:15Z","end_local":"07:15","hours":0.58,"label":"poor","mean_quality":0.15,"start":"2026-12-21T04:40Z","start_local":"06:40"},{"end":"2026-12-21T05:45Z","end_local":"07:45","hours":0.5,"label":"unusable","mean_quality":0.0,"start":"2026-12-21T05:15Z","start_local":"07:15"}]},"calculation_version":"2026-10-10.1","forecast":[],"forecast_source":"none","forecast_updated_at":null,"limits":{"good_alt":30.0,"usable_alt":20.0},"night":{"dark_from":"2026-12-20T16:33:37Z","dark_hours":11.51,"dark_to":"2026-12-21T04:04:04Z","moon":{"illumination":0.859,"phase":"waxing gibbous","waxing":true},"moon_free_dark_hours":1.47,"moonrise":"2026-12-20T11:38:07Z","moonset":"2026-12-21T02:35:26Z","sunrise":"2026-12-21T05:44:36Z","sunset":"2026-12-20T14:53:05Z","twilight":{"astronomical":{"end":"2026-12-20T16:33:37Z","start":"2026-12-21T04:04:04Z"},"civil":{"end":"2026-12-20T15:24:41Z","start":"2026-12-21T05:13:00Z"},"nautical":{"end":"2026-12-20T15:59:45Z","start":"2026-12-21T04:37:56Z"}},"window_end":"2026-12-21T10:00:00Z","window_start":"2026-12-20T10:00:00Z"},"night_date":"2026-12-20","site":{"elev_m":1750,"lat":41.693,"lon":24.739,"name":"NAO Rozhen"},"warnings":["No cloud data for this night (beyond the 4-day forecast, or not yet in the archive) \u2014 the score is geometry only."]}