Answer:
The time for Esha Salaat commences after the disappearance of the twilight and remains until before the break of dawn.
It is advisable to delay the Esha Salaat until one third of the night, permissible to delay until half the night and disliked thereafter without any valid reason in Shari?ah. Males should always perform their Salaat in congregation.
and Allah Ta’ala Knows Best
Mufti Ebrahim Desai