{"assessment":{"best_window":{"end":"2026-04-21T01:50Z","end_local":"04:50","hours":3.83,"label":"good","mean_quality":0.99,"start":"2026-04-20T22:00Z","start_local":"01:00"},"cost":{"altitude":0.0,"clouds":3.11,"darkness":2.7,"moon":0.23},"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":"Possible, with compromises","hourly":[{"alt":null,"cloud":97,"high":91,"iso":"2026-04-20T18:00Z","label":"unusable","low":23,"mid":61,"moon_alt":32,"precip":0.0,"q":0.0,"rh":96,"sky":"nautical twilight","temp":2.6,"time":"21:00","wind":4.3},{"alt":null,"cloud":90,"high":89,"iso":"2026-04-20T19:00Z","label":"unusable","low":5,"mid":2,"moon_alt":22,"precip":0.0,"q":0.0,"rh":98,"sky":"night","temp":2.0,"time":"22:00","wind":5.0},{"alt":null,"cloud":66,"high":63,"iso":"2026-04-20T20:00Z","label":"poor","low":1,"mid":4,"moon_alt":12,"precip":0.0,"q":0.25,"rh":98,"sky":"night","temp":0.8,"time":"23:00","wind":4.8},{"alt":null,"cloud":72,"high":71,"iso":"2026-04-20T21:00Z","label":"poor","low":1,"mid":1,"moon_alt":2,"precip":0.0,"q":0.19,"rh":98,"sky":"night","temp":0.2,"time":"00:00","wind":4.8},{"alt":null,"cloud":1,"high":0,"iso":"2026-04-20T22:00Z","label":"good","low":0,"mid":1,"moon_alt":-6,"precip":0.0,"q":0.99,"rh":98,"sky":"night","temp":-0.2,"time":"01:00","wind":4.9},{"alt":null,"cloud":1,"high":0,"iso":"2026-04-20T23:00Z","label":"good","low":0,"mid":1,"moon_alt":-13,"precip":0.0,"q":0.99,"rh":97,"sky":"night","temp":-0.5,"time":"02:00","wind":3.6},{"alt":null,"cloud":0,"high":0,"iso":"2026-04-21T00:00Z","label":"good","low":0,"mid":0,"moon_alt":-18,"precip":0.0,"q":1.0,"rh":91,"sky":"night","temp":-0.5,"time":"03:00","wind":4.7},{"alt":null,"cloud":1,"high":0,"iso":"2026-04-21T01:00Z","label":"good","low":1,"mid":0,"moon_alt":-21,"precip":0.0,"q":0.99,"rh":91,"sky":"night","temp":-0.8,"time":"04:00","wind":3.5},{"alt":null,"cloud":55,"high":54,"iso":"2026-04-21T02:00Z","label":"poor","low":1,"mid":0,"moon_alt":-21,"precip":0.0,"q":0.19,"rh":89,"sky":"astronomical twilight","temp":-0.6,"time":"05:00","wind":2.6},{"alt":null,"cloud":71,"high":71,"iso":"2026-04-21T03:00Z","label":"poor","low":1,"mid":0,"moon_alt":-19,"precip":0.0,"q":0.03,"rh":89,"sky":"nautical twilight","temp":-0.8,"time":"06:00","wind":2.4}],"peak_quality":1.0,"peak_sky":1.0,"quality_hours":4.46,"reasons":["cloud cover cost 3.1 quality-hours","daylight and twilight cost 2.7 quality-hours"],"reference_hours":4.0,"score":59,"score_astronomy":100,"score_weather":59,"sky_hours":7.57,"verdict":"marginal","verdict_astronomy":"good","weather_known":true,"windows":[{"end":"2026-04-20T20:00Z","end_local":"23:00","hours":2.92,"label":"unusable","mean_quality":0.0,"start":"2026-04-20T17:05Z","start_local":"20:05"},{"end":"2026-04-20T22:00Z","end_local":"01:00","hours":2.0,"label":"poor","mean_quality":0.22,"start":"2026-04-20T20:00Z","start_local":"23:00"},{"end":"2026-04-21T01:50Z","end_local":"04:50","hours":3.83,"label":"good","mean_quality":0.99,"start":"2026-04-20T22:00Z","start_local":"01:00"},{"end":"2026-04-21T02:00Z","end_local":"05:00","hours":0.17,"label":"marginal","mean_quality":0.49,"start":"2026-04-21T01:50Z","start_local":"04:50"},{"end":"2026-04-21T03:05Z","end_local":"06:05","hours":1.08,"label":"poor","mean_quality":0.12,"start":"2026-04-21T02:00Z","start_local":"05:00"},{"end":"2026-04-21T03:35Z","end_local":"06:35","hours":0.5,"label":"unusable","mean_quality":0.0,"start":"2026-04-21T03:05Z","start_local":"06:05"}]},"calculation_version":"2026-10-10.1","forecast":[{"cloud":100,"dark":false,"high":100,"local":"20:00","low":4,"mid":5,"precip":0.2,"rh":87,"temp":3.9,"time":"2026-04-20T17:00Z","wind":3.1},{"cloud":97,"dark":false,"high":91,"local":"21:00","low":23,"mid":61,"precip":0.0,"rh":96,"temp":2.6,"time":"2026-04-20T18:00Z","wind":4.3},{"cloud":90,"dark":true,"high":89,"local":"22:00","low":5,"mid":2,"precip":0.0,"rh":98,"temp":2.0,"time":"2026-04-20T19:00Z","wind":5.0},{"cloud":66,"dark":true,"high":63,"local":"23:00","low":1,"mid":4,"precip":0.0,"rh":98,"temp":0.8,"time":"2026-04-20T20:00Z","wind":4.8},{"cloud":72,"dark":true,"high":71,"local":"00:00","low":1,"mid":1,"precip":0.0,"rh":98,"temp":0.2,"time":"2026-04-20T21:00Z","wind":4.8},{"cloud":1,"dark":true,"high":0,"local":"01:00","low":0,"mid":1,"precip":0.0,"rh":98,"temp":-0.2,"time":"2026-04-20T22:00Z","wind":4.9},{"cloud":1,"dark":true,"high":0,"local":"02:00","low":0,"mid":1,"precip":0.0,"rh":97,"temp":-0.5,"time":"2026-04-20T23:00Z","wind":3.6},{"cloud":0,"dark":true,"high":0,"local":"03:00","low":0,"mid":0,"precip":0.0,"rh":91,"temp":-0.5,"time":"2026-04-21T00:00Z","wind":4.7},{"cloud":1,"dark":true,"high":0,"local":"04:00","low":1,"mid":0,"precip":0.0,"rh":91,"temp":-0.8,"time":"2026-04-21T01:00Z","wind":3.5},{"cloud":55,"dark":false,"high":54,"local":"05:00","low":1,"mid":0,"precip":0.0,"rh":89,"temp":-0.6,"time":"2026-04-21T02:00Z","wind":2.6},{"cloud":71,"dark":false,"high":71,"local":"06:00","low":1,"mid":0,"precip":0.0,"rh":89,"temp":-0.8,"time":"2026-04-21T03:00Z","wind":2.4},{"cloud":73,"dark":false,"high":73,"local":"07:00","low":0,"mid":0,"precip":0.0,"rh":90,"temp":-0.6,"time":"2026-04-21T04:00Z","wind":2.0}],"forecast_source":"history","forecast_updated_at":"2026-10-14T07:01:22Z","limits":{"good_alt":30.0,"usable_alt":20.0},"night":{"dark_from":"2026-04-20T18:49:30Z","dark_hours":7.0,"dark_to":"2026-04-21T01:49:43Z","moon":{"illumination":0.165,"phase":"waxing crescent","waxing":true},"moon_free_dark_hours":4.55,"moonrise":"2026-04-21T06:06:58Z","moonset":"2026-04-20T21:15:44Z","sunrise":"2026-04-21T03:32:07Z","sunset":"2026-04-20T17:07:03Z","twilight":{"astronomical":{"end":"2026-04-20T18:49:30Z","start":"2026-04-21T01:49:43Z"},"civil":{"end":"2026-04-20T17:36:22Z","start":"2026-04-21T03:02:50Z"},"nautical":{"end":"2026-04-20T18:11:46Z","start":"2026-04-21T02:27:26Z"}},"window_end":"2026-04-21T09:00:00Z","window_start":"2026-04-20T09:00:00Z"},"night_date":"2026-04-20","site":{"elev_m":1750,"lat":41.693,"lon":24.739,"name":"NAO Rozhen"},"warnings":[]}