Re: [ATM] refractor aberration

["Bob May" <rmay@nethere.com>]

Sounds more to me like it is a lens that isn't made correctly.
Wedge in one of the lenses will do this and you can check this by
turning the lens and seeing if the aberration moves with the
angle of the lens.
If so, I'd then disassemble the lens and see if the crown lens
has an even thickness around the edge (this is the hardest lens
to check as it is difficult to measure the edge consistently at
or near the edge).  The flint is a lot easier as you merely need
to check the edge, providing that the R4 surface is either flat
or conccave.
If you find that the distance isn't even all the way around but
rather there is a thick side and a thin side, the flint may also
have the same problem.  If so, you need to put the two lenses in
the cell so that they are aligned with their centers off in the
same d9irection.
If the lenses are cemented together, you're in trouble!
Wedge is a big problem with refractorive lenses as this basically
put a prism into the lens setas you can consider that each lens
is made up of three parts, two plano-x lenses with a flat/prism
between them in that one piece of glass.
Please note that if your measurements are all over the place, you
need to do a better job of measuring, maybe even making a jig so
that you can consistently measure the crown lens at a consistent
distance from the edge.  The measurrement should be within a
thousandth of an inch all the way around.
Good Luck!
Bob May
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