Quote Originally Posted by ic-racer View Post
Just to elaborate on another technique ...
Yet another technique:

Just suppose or postulate that if a projected image
is in form the exact of some object projected then
we can say within our context that the system
is aligned.

Based upon that postulate I've aligned my enlarger
using the square of the negative carrier as the object
for projection. At the baseboard I employ a square to
assure 90 degree agreement.

That's it. Of course the image need be well focused
for accurate use of the square. An object truly square
but smaller than the negative carrier could be the
subject for alignment. Dan