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24156Re: TMB 80mm "super" apo

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  • Jim Fusco
    Apr 1, 2005
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      Tom, correct me if im wrong there is no such word as a super
      apochromatic, It's superachromatic.


      Maybe the term super apo really means a extreamly well corrected APO?

      The lens you and Dmitry Makolkin from SilverStar Optics that TMB
      fully optimized was called a super-achromat, ED star manufacture. I
      understand this is not a fully TMB designed lens, But TMB had a
      significant input in the development of this lens to make this design
      work. I was reading a old post by you that brings me to this. But
      after reading the zeiss.de that a superachromat is a defect in a sort.
      The design works on computer but changes in the manfacture process
      keeps this the constant away and like 8 out of 10 lenses are very
      well corrected APO and the 2 left over are SAPC or meet the
      superachromatic requirements. Please correct me if my understanding
      is wrong.

      Best Regards,


      --- In tmboptical@yahoogroups.com, "tmboptical" <TMBoptical@a...>
      > --- In tmboptical@yahoogroups.com, "APM-Telescopes Markus Ludes"
      > <apm_telescopes@w...> wrote:
      > > Tom
      > >
      > > from where you have the technical specs you use for the Term
      > apo ? To my knowledge a superapo must have 4 crossings ( a normal
      apo 3
      > crossings) , and nothing additional then other apos
      > >
      > > the 80 mm design exceed the APQ design and have 4 crossings and
      > therefore LOMO called them with all rights super apo
      > >
      > > best wishes
      > > Markus
      > Markus,
      > From none other than the greatest optical scientist in the 20th
      > and also the man that came up with the term "Super Apochromat,"
      > G. Baker. In his groundbreaking article in Applied Optics, back in
      > 1963, called "Planetary Telescopes," he outlined why refractors are
      > the very best telescopes of any type, for planetary observing, and
      > in fact, showed back in the 1940's, that he was the inventor of the
      > modern triplet apochromat, where the power element made out of CaF-2
      > is in the center, and two crown elements were matched on the
      > and inside of the triplet, just like TMB, AP, Zeiss, TAK, and TEC
      > use today. His design would hold up to the best of today's designs,
      > even know it was designed over 65 years ago. It was BK-7/CaF-2/K-10,
      > a darn good true triplet apochromat.
      > He also used the term Super Apochromat to describe an apochromat,
      > that in his own words: "A Superapochromat is superachromatically
      > corrected over the full aperture for aplanation."
      > This means that for a lens to be a true Superapochromat, it must
      > not only have four color crossings, but it must be aplanatic over
      > the entire aperture (coma and spherical), which means no sphero-
      > chromatism or coma. The reason no lens reaches this level of
      > performance, and James Baker talks about this, is because you
      > need to put two higher order aspherics on two surfaces of the
      > lens, and this would no longer be a lens that could be sold
      > in any real numbers, in fact, very few master opticians can
      > do this type of figuring, and the costs would be extremely
      > high per lens. So much so, no one would buy it.
      > I recommend anyone that wants to learn more about the history of
      > apo refractors, why apo refractors are as good as they are, the
      > many different design types of apo refractors (for planetary use),
      > what the requirements are for different levels of refractor
      > correction, and what they mean, should either find a copy of his
      > article at a University library, or download it off the Internet
      > for about $15.00. It is the ultimate statement on why apo refractors
      > are the best telescopes, inch for inch.
      > Thomas Back
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