Hiper APO 152 Triplet Refractor

Optics
In all our refractors we use the highest
quality optical sets available on the market.
We�re currently using one of the best 80
mm optic on the market, the Super APO
triplet F/6 produced by LOMO and the
full APO triplet line, from 105 to over 200
mm diameter, designed by Thomas Back
and produced at LZOS factory. Some special
products are using other APO triplet
objectives developed by our optical designers
and produced with the highest
quality standards. All LZOS triplet instruments
come equipped, as standard, with
an interferometric test report. All instruments
are tested, verified and collimated
before delivery on our autocollimation
(double light passage type) optical
bench with an artificial laser star at very
high magnification.
The LZOS factory, with its huge structure
placed Near Moscow, is a recognized
reference point for the manufacture of
research instrumentation in the astronomy
field and, thanks to the absolute high
quality, especially in the professional one.
Its productive capacities allow to produce
monolithic mirrors up to various meters
of diameter, and the company is
among the very few capable of producing
special raw materials for astronomy.
Besides the life long experience of the
technicians and the very modern equipment
used, one of the most important
strong points on refracting optics manufacturing,
is the internal production of all
glasses and optic materials necessary for
the production of the finished objectives.
This allows to control the true characteristics
of light dispersion of the single glass
casting and the attainment, during the
manufacturing of the surfaces and their
assembly, of the highest expectations in
performance.
Every objective produced is mounted,
aligned and tested before delivery to Officina
Stellare directly in LZOS.
Our task, thanks to our careful mechanics
design and final assembly, is to guarantee
the attainment of the max imum theoretical
possible performances of the objective.
With the help of the page �Essay on Optics� written by Thomas
Back on his web site, we want to help the customer to
have a sharp idea of some definitions widely used on the
apochromat refractormarket.
In this text which we report below there are also some important
infos on the material used for the LZOS objectives and on
their performances.
�Apochromatism�: an old definition
With the proliferation of apochromatic refractors that are
available to the amateur astronomer, it is time to define the
parameters of a true apochromaticobjective lens.
The modern definition of "apochromat" is the following: an objective
in which the wave aberrations do not exceed 1/4
wave optical path difference (OPD) in the spectral range
from C (6563A - red) to F (4861A - blue), while the g wavelength
(4358A - violet) is 1/2 wave OPD or better, has three
widely spaced zero color crossings and is corrected for coma.
�Apochromatism�: a brief history
Abbe, working for carl Zeiss during the last years of 1800, discovered
that by using optically clear, polished natural fluorite,
in a microscope objective, the �apochromatism� could be
achieved. These first true apochromatic microscope objectives
were so superior to the competition, that Zeiss gained
nearly the entire high end market. So secret was the use of
fluorite, that Abbe marked an "X" on the data sheet for the
fluorite element, so as to keep it secret from the other optical
companies.
Abbe's definition of apochromatism was the following.
Apochromat: an objective corrected parfocally for three
widely spaced wavelengths and corrected for spherical aberration
and coma for two widely separated wavelengths.
This definition is not as simple as it sounds.
Abbe's definition, to put it in clearer terms (I hope) is that a
true apochromat is an objective that has three color crossings
that are spaced far apart in the visual spectrum (~4000A,
deep violet to ~7000A, deep red).
But what about the levels of spherical aberration at each of
these wavelengths?
Abbe, in his definition of apochromat, states that spherical
aberration must be corrected for two widely spaced wavelengths.
�Apochromatism�: searching for a definitive defintion
T.B. explain us what happens whenwe try to correct spherical
for two widely spaced wavelengths: we correct for all the
wavelengths between them too. This is called correcting for
spherochromatism (the variation of spherical aberrationwith a
change in wavelength). Obtaining this is not so simple. We
need to do a combination of a lot designs/factors. It is the
designer that must come up with a good compromise of color
correction, lack of spherical aberration (3rd order and zonal)
and controlling spherochromatism, so as not to degrade the
image contrast. All major brands use different technics: wide
air-spaced Petzval design, Fluorite and/or exotic glass, large
air spacing, slightly aspherization, etc. to control the above
aberrations.
T.M. designed LZOS objectives optical uses Russian OK-4 super
ED glass with an outer crown and a special dense crown glass,
using air spacing with different internal radii, and hand figuring
to control these aberrations.
Now you might ask, after all this, just what is a modern definition
of apochromatism?
Well, as you read, it is not only three color crossings. One of
the first things an optical designer discovers is that with catalog
glass data, it is easy to design lenses with three or even
four color crossings (superachromat).
But what is really important is how small the chromatic focal
shift is (not the zero crossings) over a wide spectral range, and
how low the spherical aberration is over that same range.
So we are left with an ambiguous definition.
After designing, testing and selling many different apochromatic
lenses T.M. remember us that there is no "definite" line
where a lens becomes "apochromatic" in the world of commercial
apochromatic lenses.
A modern definition for "apochromatic" is not so simple to
write.
No matter the kind of optical scheme we are talking about
(doublet, triplet, quad, air-spaced or Petzval).We need to talk
about Strehl ratio, coma correction, wavelength of diffraction
limited color correction, spherical aberration, good control of
the violet g wavelength and optical spot sizes that concentrate
the max imum amount of photons within the diffraction
limit. We need to talk about all this to satisfy amodern definition
of "Apochromatism."
Materials
All our refractor OTAs are made of aluminium (6061 anticorodal
� 7075 ergal) for the rear and front assembly (fully CNC
machined) and true carbon-graphite fiber for the tube (high
module true carbon-graphite fiber, obtained in high vacuum
chamber).
Each OTA is machined to the highest tolerances and is computer
optimized to be lightweight with the best structural rigidity.
The internal baffles (we use up to 7 internal baffles for the
tube, from the lens to very close to the focuser and others directly
inside the focuser) are laser cut from stainless steel and
glued to the tube with a professional glue.
The true carbon-graphite fiber allows to obtain a very stable
focus position at very large temperature variations and is very
Serie Hiper APO brochure. v.01/2010
lightweight, really useful for great diameter refractors.
Design
In our OTAs we use the original lens cell provided by the optics
manufacturer, the installation is carried out very carefully and
particular attention is used to avoid introducing any mechanical
stress on the lenses.
Our dew and light shield is fully retractable to make the tube
size very compact for transport.
We put a lot of attention in all our design to prevent any internal
reflection (using very opaque paint, even on all the laser
cut internal baffles, and black velvet on all other parts) and
scattered light. This allows to obtain the max imum performances
of the optics.
Some innovatons
In all our 130 mm and larger refractors, we are proud to announce
a very innovative solution for the problem relatedwith
the residual internal heat. This is the Officina Stellare exclusive
Cooling & Internal Seeing Stabilization System.
This system consists of:
-9 little holes, drop shaped, CNC machined on the conical
section of frontal aluminium assembly (dew shield support).
-9 little holes, drop shaped, CNC machined on the conical
section of rear aluminium assembly (focuser support).
-3 internal electrical microfans,with hand speed control
All internal baffles are redesigned and laser cut to convey the
air flux along the internal walls of the carbon-graphite tube,
without the danger of getting dust inside the tube.
Thanks to this solution, large refractors (this feature is standard