Information
Introduction
Individual production
Glass
Glass thickness
Test
Interferometry
Shipping
Introduction
Telescopes
with half a meter diameter mirror ... only a few years ago they were unthinkable
for amateur astronomers. With todays engineering, manufacturing and
materials, large Newton mirrors with more than 28 inch have become affordable
even for amateur astronomers. Telescopes with 20" (510mm) to 24" (610mm)
diameter can almost be called standard for small observatories or as mobile
telescopes with Dobson mounting.
For
most amateur astronomers, private, school and public observatories the
purchase of a telescopic mirror will have to last for many years. At Alluna
Optics you receive the correct mirror for you telescope made to meet even
the highest demands.
Clear
image of stars, high definition with highest contrast distinguish our optics.
Individual
production
You
need a 24 inch primary mirror with an opening ratio of 4,1 - no problem,
we produce your primary mirror according to your specifications. Aside
from the standard sizes we can
satisfy just about every wish from a diameter of 16 inch up to 40 inch.
Our price/quality ratio will convince you! You will hardly find a better
quality mirror at a more reasonable price!
Glass
High
quality Newton mirrors require high quality glass. Predominantly we use
precision annealed Pyrex® No. 7740 or Suprax® 8488. This glass
has a low thermal expansion and allows for an especially smooth surface.
For an appropriate surcharge we will also produce primary mirrors from
glass Ultra Low Expansion Titanium-Silicatglass ULE™ / Corning or Sitall
CO-115M.
20" Pyrex Cassegrain f2,5
Glass
thickness
We choose the glass thickness
so that distortions can appear on the surface at a normal, proper mirror
storage hardly . We use a glass strength of 40 mm for main mirrors to 16
inch of diameters, about this 50-54 mm. We recommend a glass thickness
for mirrors after 28 inches more than 70 mm. Otherwise, high requirements
on the mirror storage are necessary.
30 Inch Astro-Sitall mirror
with 3 Inch thickness
Test
A
telescope mirror is only as good as its optical face! Deviations of just
a few millionth part of a millimeter on the surface can impair the imagining
quality crucially. We conduct extensive tests during the complete production
process. Free of astigmatism, a perfect parabola and at the same time a
smooth surface all the way to the outer 
edge
of the mirror, those are the features of our parabolic mirrors. An extensive
test report including surface pictures and interferogram in digital form
accompany every mirror. We guarantee for all of our mirrors Lambda/6PV
wave, Strehl above .90.
example Certificate from
30
Inch Mirror
Interferometry
During the polishing as
well as at the beginning of parabolization the inspection of the surface
and form are conducted using the tests according to Foucault and Ronchi.
In the end phase the complete surface is measured by interferometer and
depending on the size of the mirror up to 10000 measuring points on the
surface are evaluated through the software. With the help of interferometry
the complete topography of the mirror can be measured accurately. Our tests
can be reproduced by anyone. We are most likely the only manufacturer who
is not afraid to publish the original interferograms for every completed
mirror. We examine in ROC or with Ross Null Test.
Mirror up to 24 Inch we
examine in autokollimation with high precise plan mirror.
Many mirrors are examined
directly at the star.
25 Inch Mirror f3,8
Ronchi test at the star
with a 26 lp/mm High Precision Ronchi Ruling Glass.
Shipping
Shipping
will only commence when all high quality requirements have been met. Every
primary mirror comes with a serial number and is shipped after being packed
very carefully into a sturdy wooden box. A certificate to this serial number
including the original interferogram, Foucault surface pictures and rotation
interferogram on a CD are included with the shipment.
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