Orion Optics UK ODK16 - 16" F/6.8 Optimised Dall Kirkham - Flat Field

Orion Optics UK ODK16 - 16" F/6.8 Optimised Dall-Kirkham - Flat Field

The ODK16 is in use world wide by amateurs and professionals alike.

Viewing the spot diagram will show you just how good the ODK16 presents its outstanding specification, as will all the ODK models. Orion doesn’t skimp by using just 2 lens elements in the corrector system, they could, but know from extensive computer designs that there is a real need for 3 elements to give a wider, flatter field. It costs quite a bit more to have this extra lens but, if you compare like with like spot diagrams of an ODK with a similar model on the market, the difference is noticeable and it’s there for every image you take or visual observation you make. You have the best optical performance available in an Optimised Dall-Kirkham, anywhere.

We recommend that ODK16 are observatory mounted.

ODK Optimised Dall-Kirkhams from Orion Optics UK

The full range is based on a focal ratio of f6.8, fast enough for some superb photo-visual deep-sky 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 Orion´s Precision ACU-3S 3” Crayford Focuser featuring a 10:1 reduction drive included as standard - focuser shown as fifth image. Good images need good optics, all fitted in reliable, stable and precise engineering.

Optics

All Orion UK ODK primary mirrors are made from Schott Borosilicate Low Expansion Suprax glass (virtually identical to Pyrex), as are all Orion 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, the specialists don’t release one to their coating department unless it achieves a surface accuracy of 1/6 wave or better. How do they know when they have achieved that very high degree of accuracy? They 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 know the optics’ or telescope’s performance exactly. 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.

Tube Rings

To give maximum security and exactness, Orion Optics manufacture, on their own CNC milling machines, aluminium tube rings which are machined from solid pieces of aluminium and later black anodised to protect the surface which are felt lined to give a gentle but firm grip to the polished tubes. Pressure adjustment is made by the large knurled knob on each tube ring to give precise amounts of friction on the tube outer surface.

ACU-3S Focuser

The ODK series of Optimised Dall-Kirkhams is supported by a precision 3” focuser of short draw tube length. The top of the draw tube is threaded to accept many accessories, adaptors and spacing components. Silky smooth, incredible strength and attractive looks give you all the reliability and confidence in the ACU-3S you are ever likely to need. 3” draw tube (76.2 mm) enables wide fields to be achieved with vignetting not being a problem. Ultra accurate 10:1 slow motion control with a smooth, effortless motion which has got to be tried to be believed. Carrying capacity way beyond the requirements of all but the heaviest cameras.

The focuser is connected the telescope by means of a very accurate machined female dovetail which is held onto a male equivalent on the telescope tube or cell with stainless steel grub screws. The beauty of this arrangement is that these screws and dovetail coupling allow you to rotate the focuser through 360 degrees rotation. In other words, to put it in exactly the rotational position you want for the attached equipment fitted, CCD, filter wheels, guiders etc. It just makes it so easy to set things up perfectly to meet your needs.

Astrophotographic results obtained with this telescope on Astrobin

Here you can find some astrophotographs made with this telescope model: Link to Astrobin

Astrophotographic results obtained with this telescope on Astrobin

Here you can find some astrophotographs made with this telescope model: Link to Astrobin

The surfaces of mirrors - Information from Orion UK

Manufacturing precision optical surfaces, (in this category we include both mirrors and corrector lenses), involves many specialised procedures to achieve the high degree of optical precision, some of which occasionally leave surface blemishes on the optic (mirror and/or lens).

If there are a few sleeks or scratches on the optics’ surface they in no way effect the performance of the lens or mirror either visually or photographically and cannot be considered as an acceptable reason for any complaint. Small pits are occasionally visible due to processing in the polishing and figuring process, these again cannot be accepted as reason for complaint. We endeavour to have blemish free surfaces but cannot guarantee such. Accordingly, we have set our cosmetic surface finish at a high standard production tolerance as is practical. We apply an optics industry standard to our surfaces of 80/50 scratch dig which is a measure of an acceptable level of surface blemishes per optic is acceptable.