24156Re: TMB 80mm "super" apo
- Apr 1, 2005Tom, 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
--- In firstname.lastname@example.org, "tmboptical" <TMBoptical@a...>
> --- In email@example.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 normalapo 3
> crossings) , and nothing additional then other aposcentury,
> > 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
> From none other than the greatest optical scientist in the 20th
> and also the man that came up with the term "Super Apochromat,"James
> G. Baker. In his groundbreaking article in Applied Optics, back inoutside
> 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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