Answered by Shaykh Faraz Rabbani
Recently in a discussion a brother said that the legal reason for Isha prayer is the ending of Twilight, and when there is no end of Twilight as nowadays in UK the obligation of praying is abrogated. Is this view correct and could you please explain if you have heard this before, so I can explain to the brother.
This is not correct.
The chosen position (as mentioned by Ibn Abidin in his Radd al-Muhtar) is that even in those lands where there is no Isha time, Isha prayer remains obligatory, and people must determine its time [by the nearest area that has Isha time].
There are two twilights:
(a) the disappearance of the whiteness in the sky. This is the position of Abu Hanifa, and leads to ‘late’ Isha times (18 degrees on calendars);
(b) the disappearance of the redness in the sky. This is the position of Abu Hanifa’s main students, Abu Yusuf and Muhammad ibn al-Hasan, and most late scholars chose this. It leads to earlier Isha times (12 degrees on calendars).