That is what I meant. Where is the justification to follow the second calculation method (dividing the night in 7 parts) in August, September and October, when 18 degrees and 15 degrees are clearly entering in that particular city? How can you use alternative calculations when the time of Isha is still entering? Who from the Ulama has allowed that and based on what classical texts? The same Ulama who hammer on 18 degrees for Fajr are very soft when it comes to following 15/18 degrees for Isha.