{"assessment":{"best_window":{"end":"2027-09-13T02:25Z","end_local":"05:25","hours":1.67,"label":"good","mean_quality":0.88,"start":"2027-09-13T00:45Z","start_local":"03:45"},"cost":{"altitude":0.0,"clouds":0.0,"darkness":2.49,"moon":3.75},"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":"2027-09-12T17:00Z","label":"unusable","low":null,"mid":null,"moon_alt":18,"precip":null,"q":0.0,"rh":null,"sky":"civil twilight","temp":null,"time":"20:00","wind":null},{"alt":null,"cloud":null,"high":null,"iso":"2027-09-12T18:00Z","label":"poor","low":null,"mid":null,"moon_alt":25,"precip":null,"q":0.24,"rh":null,"sky":"astronomical twilight","temp":null,"time":"21:00","wind":null},{"alt":null,"cloud":null,"high":null,"iso":"2027-09-12T19:00Z","label":"marginal","low":null,"mid":null,"moon_alt":30,"precip":null,"q":0.45,"rh":null,"sky":"night","temp":null,"time":"22:00","wind":null},{"alt":null,"cloud":null,"high":null,"iso":"2027-09-12T20:00Z","label":"marginal","low":null,"mid":null,"moon_alt":32,"precip":null,"q":0.44,"rh":null,"sky":"night","temp":null,"time":"23:00","wind":null},{"alt":null,"cloud":null,"high":null,"iso":"2027-09-12T21:00Z","label":"marginal","low":null,"mid":null,"moon_alt":31,"precip":null,"q":0.45,"rh":null,"sky":"night","temp":null,"time":"00:00","wind":null},{"alt":null,"cloud":null,"high":null,"iso":"2027-09-12T22:00Z","label":"marginal","low":null,"mid":null,"moon_alt":26,"precip":null,"q":0.47,"rh":null,"sky":"night","temp":null,"time":"01:00","wind":null},{"alt":null,"cloud":null,"high":null,"iso":"2027-09-12T23:00Z","label":"marginal","low":null,"mid":null,"moon_alt":20,"precip":null,"q":0.51,"rh":null,"sky":"night","temp":null,"time":"02:00","wind":null},{"alt":null,"cloud":null,"high":null,"iso":"2027-09-13T00:00Z","label":"marginal","low":null,"mid":null,"moon_alt":12,"precip":null,"q":0.56,"rh":null,"sky":"night","temp":null,"time":"03:00","wind":null},{"alt":null,"cloud":null,"high":null,"iso":"2027-09-13T01:00Z","label":"good","low":null,"mid":null,"moon_alt":2,"precip":null,"q":0.62,"rh":null,"sky":"night","temp":null,"time":"04:00","wind":null},{"alt":null,"cloud":null,"high":null,"iso":"2027-09-13T02:00Z","label":"good","low":null,"mid":null,"moon_alt":-8,"precip":null,"q":1.0,"rh":null,"sky":"night","temp":null,"time":"05:00","wind":null},{"alt":null,"cloud":null,"high":null,"iso":"2027-09-13T03:00Z","label":"poor","low":null,"mid":null,"moon_alt":-18,"precip":null,"q":0.15,"rh":null,"sky":"nautical twilight","temp":null,"time":"06:00","wind":null}],"peak_quality":1.0,"peak_sky":1.0,"quality_hours":5.18,"reasons":["moonlight cost 3.7 quality-hours","daylight and twilight cost 2.5 quality-hours"],"reference_hours":4.0,"score":null,"score_astronomy":100,"score_weather":null,"sky_hours":5.18,"verdict":"unknown","verdict_astronomy":"good","weather_known":false,"windows":[{"end":"2027-09-12T17:05Z","end_local":"20:05","hours":0.5,"label":"unusable","mean_quality":0.0,"start":"2027-09-12T16:35Z","start_local":"19:35"},{"end":"2027-09-12T18:15Z","end_local":"21:15","hours":1.17,"label":"poor","mean_quality":0.16,"start":"2027-09-12T17:05Z","start_local":"20:05"},{"end":"2027-09-13T00:45Z","end_local":"03:45","hours":6.5,"label":"marginal","mean_quality":0.48,"start":"2027-09-12T18:15Z","start_local":"21:15"},{"end":"2027-09-13T02:25Z","end_local":"05:25","hours":1.67,"label":"good","mean_quality":0.88,"start":"2027-09-13T00:45Z","start_local":"03:45"},{"end":"2027-09-13T03:00Z","end_local":"06:00","hours":0.58,"label":"marginal","mean_quality":0.5,"start":"2027-09-13T02:25Z","start_local":"05:25"},{"end":"2027-09-13T03:35Z","end_local":"06:35","hours":0.58,"label":"poor","mean_quality":0.15,"start":"2027-09-13T03:00Z","start_local":"06:00"},{"end":"2027-09-13T04:00Z","end_local":"07:00","hours":0.42,"label":"unusable","mean_quality":0.0,"start":"2027-09-13T03:35Z","start_local":"06:35"}]},"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":"2027-09-12T18:11:32Z","dark_hours":8.2,"dark_to":"2027-09-13T02:23:32Z","moon":{"illumination":0.917,"phase":"waxing gibbous","waxing":true},"moon_free_dark_hours":1.15,"moonrise":"2027-09-12T15:05:15Z","moonset":"2027-09-13T01:13:20Z","sunrise":"2027-09-13T03:58:47Z","sunset":"2027-09-12T16:36:23Z","twilight":{"astronomical":{"end":"2027-09-12T18:11:32Z","start":"2027-09-13T02:23:32Z"},"civil":{"end":"2027-09-12T17:04:21Z","start":"2027-09-13T03:30:47Z"},"nautical":{"end":"2027-09-12T17:37:25Z","start":"2027-09-13T02:57:41Z"}},"window_end":"2027-09-13T09:00:00Z","window_start":"2027-09-12T09:00:00Z"},"night_date":"2027-09-12","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."]}