This adjustment can be done with greater precision using a single beam
collimator.

Good point Howie. I would only add that it's difficult, at least with
my Protostar assembly, to lock the secondary's rotation in the correct
position. I have to hold it in place by hand while tightening the
nut, otherwise the secondary will rotate as I'm tightening. It's hard
to tell if I held it perfectly still while tightening. Is there a way
around this problem? I'm sure many others have experienced it too.
"Getting it close" may be the best we can do for field illumination!

Ritesh