السلام عليكم ورحمة الله وبركاته أحسن الله إليكم Does Isha begin at the end of the astronomical or civil twilight? Or do you know the degree of the sun at the time of Isha? Like for example is it 18°? There is a difference between the masajid and I don't know of any person specialized in this.

Ustadh AbdulAziz al-Haqqan

And when the red twilight disappears, that's when Isha time starts.