"Bob May" wrote in message
...
Depends upon what you are doing. If you are spacing the two elements then
such a thing is a good start for the collimation. However, the end of the
tube isn't necessarily square with the optical axis of the optics so you
need to check and adjust if necessary the optics themselves. The
reflections of light from the various element surfaces is generally the
right way for a lens to get the surfaces coaxial to the tube.

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My elements are cemented together with 3 foil-like spacers at 120 deg. The
elements
are held down by a screw-in retainer ring. This I believe brings the lens
into a symmetric
position on the cell and holds it down flush to the cell body.

How can one use the reflection technique? Any directions? Thanks.