ODK20 f/6.8 Optimised Dall-Kirkham


ODK20 f/6.8 Optimised Dall-Kirkham

Regular price
$ 33,499.00
Sale price
$ 33,499.00
Unit price

This item is a Special Order from the Manufacturer

Special Order


The full range is based on a focal ratio of f6.8, fast enough for some superb deep sky photo-visual use and, still have enough focal length for high resolution planetary work both visual and CCD applications.

The tube is constructed from Carbon Fibre sandwich design. Very, very strong to avoid flexing and, zero expansion to ensure the focal plane does not change over long photographic exposures. Being an open tube design and very short, cool down times are remarkably fast.

To assist cool down of the telescope, each model is fitted with three fans, all positioned behind the primary mirror.

Exact focusing across the ODK range is achieved with a Starlight Instruments FTF301B-A Feather Touch 3 Inch dual speed focuser included as standard - pictured below right. 
Good images need good optics, all fitted in reliable, stable and precise engineering.

Customers with heavier than normal (4kg+) CCD equipment can add features to the ODK tube to enhance stability.

ODK Light Path Diagram

To produce the photo-visual wide, flat field of the ODK range, we have designed and fitted integrally, a corrector lens system. which ensure both colour correction, coma and spherical aberration are optimised to achieve almost a perfect photographic and visual field. Adequate back focus allows all modern CCD cameras to be used with auxiliary equipment. Multi layer anti reflection coatings are applied to all lens surfaces to maintain brighter images.

CNC machined mono construction secondary spider and trim ensures stability in collimation. Our unique collimation adjustment system enables perfect collimation of the secondary mirror to be achieved, quickly and reliably.

All our ODK primary mirrors are made from Schott Borosilicate Low Expansion Suprax glass (virtually identical to Pyrex), as are all our primary mirrors on all ranges of telescopes. The mirrors are all produced to exacting standards to an F4 paraboloid configuration. How exact are they? Well, we don’t release one to our coating department unless it achieves a surface accuracy of 1/6 wave or better. How do we know when we have achieved that very high degree of accuracy? 
We use one of the worlds most exacting measuring devices, a Zygo Laser Interferometer. Take a few minutes and visit the Zygo page and be amazed at just how good this machine is at measuring optics, it can measure optical distances which are smaller than 2,000, yes, 2,000 times smaller than the thickness of a human hair.

Without a Zygo or similarly accurate and reliable measuring instrument, it is impossible to give accurate measurements of an optics’ or telescope’s performance. Only the best manufacturers in the business of making telescopes use them because they are not suitable for mass produced telescopes, they are slow to use and need highly skilled technicians to operate them, it just does not lend itself to anything other than the highest quality, hand figured optics, definitely not mass produced optics to a tight budget.

Primary mirrors are Hilux coated for the highest possible aluminium protected reflective surfaces available.

ODK 20

Because of many, many possible clients asking us for a larger model in the ODK range we can now offer a 500mm model with a carbon truss type tube.

Two similar models to the one we have now in production have been supplied to the ESO and ENO observatories.

Brief specification of the ODK20 is shown it the table top right, it is indeed a marvellous instrument and is based around a design which has supplied data to assist in the control of these two enormous main instruments iat the Canary Islands and Paranal observatories.

As a minimum we recommend a Paramount ME II to compliment the ‘scope or mount with similar carrying capacity.

We expect to customise several aspects of every model to your own specifications. We do not wish to impose a fixed design if a few modifications could suit your needs better.






Focal length


Focal Ratio


Tube Weight (inc. 
mount plate/dovetail)


Central Obstruction

39% of the Primary
Mirror Diameter

Back Focus from
Cell outer surface


OTA Length


Tube Material

Carbon fibre and
Carbon fibre struts

Primary Mirror Dia.


Primary Mounting

Collimated and Fixed

Primary Material

Schott Suprax

Primary Coating/Shape

Hilux 97%

Secondary Mirror Dia.


Secondary Material

Schott Suprax

Secondary Coating/Shape

Hilux 97%

Lens Group Dia.


No. of Lenses


Lens Group Coating

AR Coatings

Note: All USA AG 'scopes are supplied with adapters to connect to Starlight Instruments focusers. Focusers are NOT supplied with the telescope but are available as an 'add on'. Images used are for aesthetic appearance only.

Optional Dew Shield available - this is a matching, lightweight carbon fibre addition to help curb the onset of condensation in damp prone atmospheric climes. It is fitted or removed literally in less than a minute and greatly reduces the heavy dew precipitation which can so easily ruin what could be a classic imaging session.


Personal Upgrade Path

Buy risk-free: When it’s time to trade up you’ll get the most value for your used gear.