From: "CSC" 
To: "Atm" 
Reply-To: "CSC" 


Most objectives are positive crown front, negative flint rear. Typically,
the V mark system is there to make sure the lenses are edge aligned and
facing the right direction.  There is only one way to arrange the marks to
make a complete v, and the apex of the v is pointed at the sky.  This
should give the flattest surface to the eyepiece, and the curve to the sky.

-----Original Message-----
From: owner-atm{at}shore.net [mailto:owner-atm{at}shore.net]On Behalf Of
Hugues.Laroche{at}ses-astra.com
Sent: Monday, August 04, 2003 9:54 AM To: atm{at}shore.net
Subject: ATM Dummy refractor question...



Hi List,

Quite a bit of time ago, I acquired an achromatic doublet, thinking about
making a refractor of it. For health reasons I had to keep from large
projects in the last months which gave me time to finally assemble this
refractor.

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.

Any idea? TIA, and clear skies,

Hugues
Luxembourg




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