The ideal time for praying the morning service is to have the Amidah at sunrise. O Ch 89 (1) . The Mishnah Beruroh (1) there says that in the winter when one goes to synagogue early, one should still wait for sunrise. But if one has to travel or there is some other unavoidable circumstance one may pray earlier.
There is a concept of having a fixed place for praying O Ch 90 (19).
If one's synagogue has three morning services. At this time of the year only the last one gives one the possibility of saying the Amidah at sunrise or later. (The others have the Amidah before sunrise.)
On a normal day, one must pray at an early time in order to be at work on time. So one has a regular minyan that he attends. On a day when he can go to work later, is he obliged to go to the later (and not his regular) service where he may not feel so comfortable?
Can we extend the concept of “fixed place for praying” to mean the same time of service? Do we find any sources dealing with this question because my friend asked this question of his Rabbi and was told he could stick with his regular minyan?