ATM stopping a newtonian.

["Sam Michael" <samm@idcomm.com>]

Why is it that we do not stop the aperture of a newtonian to be the same
size as the mirror.  If one has a 6" mirror in an 8" tube.  Shouldn't one
stop the aperature at something much closer to 6"?

I am looking at baffeling a newtonian and am confused as to why the tube end
is left large.  This would seem to allow off-axis light to enter the tube
and hit the mirror...

I am sure I am going to kick myself when I hear the answer.

Sam.