I know that in Chabad yeshivas/communities a lot of peoples are davening longer (b'arichus): They are beginning hodu with the minyan and during tefila stopping to concentrate on the word and the maamar of the morning. Sometimes in the winter some mashpiim/chassidim are davening until like 1 hour before shkia.
But I heard on other chassidus that they are beginning shachris after chatzos l'chatchila
- I wanted to know on where is the source of beginning shachris after chatzos l'chatchila?
- and what are the limits of praying b'arichus?