From: "Jerry" 
To: , 
Reply-To: "Jerry" 




-----Original Message-----
 To the point: I realised that I never questioned in which order should the
2 lenses come? The positive element first, the negative or is it indifferent?

This is an air spaced doublet, with 3 small spacers glued near the edge of
one surface and some marks on the edge allowing to know which surfaces
should come close together. I do not know if it is conventional, but these
marks make a V on the edge of the doublet: as if it figured how the light
rays should converge.

Hugues
Luxembourg

Well, you have a clue with the three spacers on one surface. That most
likely an interior surface and the spacers are for space between elements.
But you can't be sure.

The V's may be meant to align like >< . My guess is that is the way
it was intended. But that is up to whoever marked it and for what reason.

The flattest of the four surfaces' is probably the back surface closest to
the eyepiece. One surface of the four is probably quite close to flat. The
surface of the positive with shortest radius curve will usually be the
surface toward the negative and will closely match the curve of the
negative element.

I would say that it goes together V's pointing at each other and flattest
surface to the eyepiece is the way to start.

Jerry

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