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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. 

Sitall mirror
 


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. 

Sitall mirror - Alluna Optics
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.

Mirror Ronchi Test
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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20 inch  High performance mirror
covered with 94% aluminum and
plasma protective layer
 


Mobile Dobson, here with uncoated
primary mirror. Such a 20 inch f4,2 
telescope can be set up by only one
person in five minutes and when
ismantled fits into any car with
loading space. Without a ladder one
can observe almost into the zenith
 


25 inch f3,8 Dobson
 


Comparison 6" to a 28" Newton
primary mirror
 


Polish of a 24" parabolic mirror 
 


Middle-hole cut with high pressure water
 


Foucault photo of a parabolic
mirror. A mirror with such a flawless surface and a perfect 
parabola leaves nothing to be 
esired....
 


Foucault in Autokollimation
 


laser interferogram in ROC
 


laser interferogram in Kompensation