I am confused about your claim that 90 minutes after sunset is the time for Isha'.

Answer

Every kitaab of Fiqh from the age of the Taabieen to this day supports our view. We do not go by any degree theory, neither 15 nor 18 degrees. We ascertain the time for Isha'

Salaat by physical observation of the phenomenon called Shufaq Abyadh or the whitish glow in the western horizon. When this disappears, then it is Isha time. This disappearance in our region takes place long before 90 minutes. In fact, even after an hour it will be Isha' time at our place. In terms of all four Math-habs, 90 minutes is way beyond the commencement of Isha' time. To ascertain the Isha' time, you should observe the phenomenon physically, and confound the stupid degree theory. The Sahaabah, Taabieeen and Tab-e-Taabieen did not teach the Ummah some confounded degree theory by means of which to determine Salaat times. The Shariah has presented its own methods which Muslims have discarded, hence they are trapped in confusion especially in Britain and the U.S.A. – the confusion of vacillating between 15 and 18 degree resulting in a difference of hours for Subh Saadiq.