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Ritchey-Chrétien Telescopes
Alluna Ritchey-Chrétien telescopes with two hyperbolic mirrors convince with their outstanding universal properties. The compact design along with low weight, colour purity, planar field free of coma and astigmatism with 65 mm in diameter. Smallest possible spot diameter up to the outer edges of the image field. All components, optics, mechanics and software meet highest quality standards. The robust CNC machined Aluminium Carbon Truss tube guarantees high adjustment stability and easy handling. All major tube components feature a complex honeycomb pocket structure, allowing us to realise an extremely lightweight yet higly stable tube. 

Since the Ritchey-Chrétien is a system with two mirrors, it has no chromatic aberration, hence it can be used throughout the entire spectrum from ultraviolet to the long-wave infrared (100nm-12mu). Through the excellent image quality, on-and off-axis, the large usable field and the versatility of a Ritchey-Chrétien system are our RC-telescopes are particularly suitable for being applied in astrophotography and the wide range of astronomical research. The RC telescopes are also a great visual instrument and thus are also well suitable for observatories serving the public.

Alluna Ritchey-Chretien Telescope are designed without compromise on optical and mechanical quality. Moreover, a Alluna Ritchey Chrétien telescope already comes with important components such as the Telescope Control System (TCS) and a high precision secondary mirror focusing.

The high precision focusing of the secondary mirror that is included in delivery allows to connect the 100 mm exit at the back side fixed and absolutely shake/bending-free with the telescope. Instrument loads such as CCD-Cameras or Spectrometer of more than 12 kilograms ask because there is no problem. In special design already implemented instrument loads on the back of more than 30 kg. Contrary to telescopes using a mechanical Focusers at the exit no deflexion or shaky connections through heavy weight of, for example a heavy CCD camera may occur.
The secondary focuser features a resolution of 3936 digits per 1 mm, corresponding to a mathematical step width of rounded 0.25µ on Secondary mirror respectively 0,0019 mm on CCD-Chip !

Alluna RC Optics
Every single mirror set is being manufactured and tested with extreme precision and care in our own production. As a matter of course we deliver a detailed certificate with interferogram with every telescope.
Alluna Ritchey Chretien telescopes can be used with a large usable field without corrector lenses. For large CCD-Cameras a Flat Field Corrector and a Flat Field Reducer is available.

Using the double lens Alluna Flat Field Corrector (AFFC) allow to use a planar field of 65 mm in diameter free of coma and astigmatism for photographic purposes. The usual lens size of 400 to 700 nm has been increased to  400 - 900 nm. You will receive an outstanding and future-proof optics perfectly suitable for bigger 45x45 mm CCD chips of the newest generation, too. Looking through our RC telescopes is visually impressive, the sharp and coma-free picture will convince you and your visitors.

For focal length reduction is a 4 Inch .74 x reducer-corrector (AFFR) available. The focal length is reduced from f8,0 to f6,0. The field is fully corrected of 60 mm

The spot diagram shows the fully corrected and flat 65 mm field which is achieved with the Alluna AFFC corrector. The RMS radius is 32 mm from the optical axis of less than 2 microns. Please note that the box size is only 14.

Spot Diagramm 20 Zoll Alluna RC Optic

Spot diagrams composite 486-656 nm sample at 20 inches Alluna RC

Alluna RC Truss OTA
The optical performance, the accuracy, reliability, and the demand for highest quality aren't left to chance with Alluna Ritchey-Chrétien telescopes! 
As it is common in many other technical areas, too, we make of the indispensable support of modern CAD specifically optimised for construction and design of our systems. Complex single components and sub-assemblies are modelled exactly upon the requirements and assembled virtually before production. 
RC OTA Modellierung CAD
OTA modeling in CAD
Finite element analysis Supporting components

Thus, all parts can be optimised in advance with regard to weight, stability and expansion behaviour. The comprehensive FEA (Finite element analysis) additionally helps to analyse all supporting parts by means of a stress simulation, thus being an important tool for a target-oriented construction. 
Construction data derived from CAD are “directly” transmitted to the currently most advanced CNC production machines and the precision elements required for our OTAs are produced with a precision of a hundredth of a millimeter. All parts are matching and fit to each other down to the last detail.

Alluna Telescope Control System TCS
Alluna TCS - Telescope Control SystemYou may cooncentrate on your astro shots or research work while the Telescope Control System (TCS) will take care of the basic functions of your telescope. On the one hand climatisation ot the optical tube and the main mirror, on the other hande focussing of the optics.

The climate mode also provides exact temperature data. Controlling the fans is fully automated, depending on the current delta between surrounding temperature and main mirror temperature. The focus mode displays the current focus position in Teleskopes Control Systemdigits, mm or inches on a large-sized display. The GoTo function allows you to approach pre-set focus positions fast and precise. The so-called focus drift is automatically compensated. In addition, the Telescope Control System features the  so-called CCD rotator mode including all functions required for a comfortably and precisely controlling this extremely helpful tool for all astrofotographers.  For a detailed explanation of all Telescope Control System functions, please refer to the corresponding product page.


Watch Alluna RC-Telescopes video information

Basic information about Alluna RC
- Available sizes: 16 / 18 / 20 / 24 inches f 8,0 system 
- Real Ritchey-Chrétien telescope with two hyperbolic mirrors 
- Quality Alluna optics selectable Pyrex or glass ceramics Zerodur
- Optics interferometrically tested and certified
- High-quality aluminium coating with SIO protective layer 
- AFFC 4" Field corrector - flattened, coma/astigmatism-free field of 65 mm diameter, annealed 400-900 nm
- AFFR 4" Reducer Corrector x.74, coma/astigmatism-free field of 65 mm diameter, annealed 400-700 nm
- Future-proof, also suitable for the bigger CCD chips of the new generation 
- max. spot radius: 1.5 micron rms 25 mm off-axis / 486-656 nm (AFFC)
- Applicable from ultraviolet to infrared
- Large-sized back focus area of 355 mm  from mkirror, 250 mm from backplate.
- weight-reduced, honeycomb structure, warp-resistant carbon / aluminium CNC truss tube 
- easy adjustment and collimations free, Manual
- vignetting-free through large 4-inch connection and optimized Baffle System
- Secondary mirror focussing with position memory, automatic focus positioning, automatic focus-drift compensation 
- OneView temperature monitor, automatic fan control 
- Telescope control system for automatically monitoring focus, temperature, robotic Dust Cover, CCD precision rotator on your PC Info
- Ready for image field rotator  Info
- Only one USB cable for controlling the entire telescope, ASCOM interface 
- absolutely high-quality optics, mechanics and software; Complete manufacturing " Made in Germany " 

Technical Data Alluna Ritchey Chrétien Teleskope
Alluna RC 16
Alluna RC 18
Alluna RC 20
Alluna RC 24
Main Mirror
16 Inch / 415 mm
18 Inch / 465 mm
20 Inch / 515 mm
24 Inch / 610 mm
Main Mirror Aperture
System Aperture
Sekundär Mirror
158 mm
166 mm
185 mm
215 mm
Obstruction %
Back Focus
353 mm
350 mm
355 mm
355 mm
46 kg
60 kg
79 kg
120 kg
RC Field Corrector f 8,0
corrected field: 65 mm
2 lenses 95 mm
2 lenses 95 mm
2 lenses 95 mm
2 lenses 95 mm
RC Reducer f 8,0 to f 6,0
corrected field: 60 mm
3 lenses 93 mm
3 lenses 93 mm
3 lenses 93 mm
3 lenses 93 mm

Optional and Prices
Prices & Accessories

RC Telescopes
Ritchey-Chrétien Telescops
    *  RC 16 technical data
    *  RC 18 technical data
    *  RC 20 technical data
    *  RC 24 technical data
    *  Prices & Accessories
    *  Telescope Controll System
    *  Precision Instrument Rotator
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Alluna Ritchey Chretien Telescope
in motion

Ritchey Chrétien or Dall Kirkham
... the differences

Easy collimation of a Alluna
Ritchey Chrétien Telescope


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Alluna Optics RC16 on Paramount ME - observatory Taiwan

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Alluna RC20 at 1,5 meter Kanata telescope / Japan

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Alluna Optics RC16 on Astro Physics 1200GTO / Germany

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Alluna Optics RC20 on ASA DDM160 - Atatürk University Erzurum / Turkey