This area is fully editable and gives you the opportunity to go into more detail about your business, what you do and what sets you apart from the competition.

This area is fully editable and gives you the opportunity to go into more detail about your business, what you do and what sets you apart from the competition.

This area is fully editable and gives you the opportunity to go into more detail about your business, what you do and what sets you apart from the competition.


A completely different system was needed. Therefore, the converging rays from the plano-convex objective lens were allowed to focus, and then cross over. The emerging rays were then re-focused with a field lens followed by a series of corrector lenses to remove the remaining aberrations. This system is referred to a retrofocally corrected dialyte refractor. This produces a long instrument, so fold flats are employed to make it much more compact. This is the basic configuration of the 'Zerochromat' telescope. As the angle of the fold flats is very small (approximately 3 degrees), they can have several wavelengths of power with no loss in performance at all. However, they are made to have better than 1/10 wave irregularity to ensure optimum performance. This design is pure refractor, as the fold mirrors do just that and do not take part in the optical design. There should be no confusion, as this is not catadioptric, unlike the Schupmann design, which is not a pure refractor.
The basic idea of a dialyte system is over 150 years old, and it employs a positive singlet crown glass objective lens with a smaller flint negative lens approximately half-way between the objective lens and the focus. This was because large pieces of flint glass were very difficult to make at that time. To overcome the lateral colour problem inherent in this design, Schupmann used a small Mangin mirror (rear surface silvered) to correct for most of the aberrations. This did, however, introduce astigmatism and  resulted in a rather intolerant system ('tweaky'). More details are available on the internet.



At £7000, inclusive of VAT, the price is remarkably attractive compared with other 8 inch apochromatic refractors in the market. A traditional apochromatic 8 inch refractor is an eye-watering 36,800 Euros. Visually, there is no discernible difference between their apochromat instrument and our Zerochromat instrument on planetary detail and stars. 
The standard version of the 255mm (10 inch) f12 Zerochromat is currently £15000, inclusive of VAT. It is optimised for the visible range, from 486nm to 610nm. The 'Super' 255mm f12 Zerochromat version is currently £22000 (US$25000) inclusive of VAT. It is optimised from 400nm to 750nm, with a perfectly flat field of view over 0.8 degrees.
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As described above, the original concept of the 'Zerochromat' astronomical telescope employed a single plano-convex objective lens, and after the converging rays have crossed over, a field lens brings the rays back to focus followed by a series of corrector lenses. These  comprised two single positive lenses, a negative lens, a doublet lens and a triplet lens. 

Over time, the design has been dramatically improved; it now has fewer lenses, and no longer uses fluorite glass in the corrector elements. The theoretical Strehl ratio has now been increased to 0.995, and star tests prove this out. The corrector system now has one singlet field lens and two small doublets. Stars are tiny pin-points across the entire field of view. The field of view has increased from 0.6 degrees to nearly 1 degree. The cost has been radically reduced, and it is now possible to offer a top-class apochromatic instrument at a price that no other refractor manufacturer can get close to. 

One very useful aspect of the thin objective lens (just 12mm in the centre for the 203mm version), is a very rapid cool-down time. In a fraction of the time taken for most telescopes to cool down, you can be up and observing with no fuss. The carbon fibre tube has very low thermal expansion, and almost exactly compensates for the change in focal length of the objective lens with temperature. Over a 40 degree Centigrade change in temperature, the objective lens changes by 0.35mm in focal length. Over a similar temperature change, the composite carbon fibre tube changes by approximately 0.13mm in the opposite direction. When this is multiplied by three, because of the light path being folded, the change is 0.39mm, therefore the overall change is a mere 0.04mm.

Most of the optical work is done at our North Wales workshop, so costs have been slashed to a very affordable level, and an exceptionally high quality can be maintained. An 8 inch achromat from a well-known manufacturer can be purchased for approximately 8,000 Euros, with their 8 inch apochromatic offering at over 35,000 Euros. If money is no object, a Takahashi 200mm refractor on an observatory mount is being offered at US$167,450! However, a Zerochromat 203mm refractor on an NEQ6 mount will give precisely the same visual quality at less than 1/20 the price.
The weight of these instruments is only 12kg (26lb), which is half that of a typical 8 inch achromat, and nearly 1/3 that of an 8 inch apochromat. Mounts such as the EQ6 can easily handle the 'Zerochromat' telescope. The tube length is 1525mm, so it is easily transported in a medium-sized car. Only one person is required to set up these telescopes, unlike any other refractor of similar aperture. A useful feature is that the weight is towards the rear of the instrument, so it balances roughly 1/3 of the way from the eyepiece end. We supply these instruments in a handsome black painted birch ply and aluminium flight case, which is foam lined for safety. The dimensions are: length 1800mm, width 440mm, height 380mm.

We are now able to offer full-spectrum (400nm to 750nm) apochromatic refractors, from 255mm aperture to 560mm aperture which are diffraction-limited across a completely flat field greater than 0.6 degrees. The weights are less than half that of  traditional instruments, cool-down times are much shorter, and prices are a small fraction of traditional instruments. Standard Zerochromat refractors are optimised for the visual region, from 480nm to 610nm, but can be employed for imaging if suitable filters are used.

An 8 inch refractor is a very desirable instrument, as stated by the late Dr Patrick Moore in one of his books. We can now make this a very affordable goal to achieve at an extremely attractive price. 

  1. ​Report from customer in the Czech Republic (edited).
    Quality of picture is very good. Vega is in a centre FOV and I cannot see any CA on magnification 100x (Panoptic 24mm). Stars are pinpoint from edge to edge, also in Panoptic 35mm. The sky is rather bright (20.35 MSA), but I can see NGC 6992, 6960 without problem, after that, much better with Lumicon Deep Sky filter. Globular M15 is beautiful and I can resolve lot of stars in it. The telescope resolves Epsilon Lyrae without problem with small magnification. Colours on the stars are very good visible (like Albiero). I test Zerochromat and TEC 140 side by side today. Zerochromat again WINS. It has better resolution, more stable picture and flat whole FOV. The Zerochromat has a very good time to cool down time, I assume 10°C about 2 hours. The objective lens cools down very quickly, faster than achromat lens. The Zerochromat is very good also for DSO like a galaxy, a globular, a cluster and a nebulas. I tested a few 2" star pairs, very nice resolution with Airy disks. I will test some 0.6" pairs. I am back from a 3 days astronomy party in our country. I was very surprised from the telescope and it has very good optical design. I observed a lot of objects last night. The telescope has flat FOV and stars are pinpoint from edge to edge in my 35mm and 25mm Panoptic eyepieces. Nebula like M42, M17, M16 or small planetary nebula looks like from a much larger telescope than 200mm. Today I observe the Sun with my friends (I use 35mm Panoptic and Zeiss Mark V binocular head with two 25mm Panoptic). They say, "fantastic picture". I make a picture, but original from an eyepiece is much better. I can say, TEC 140 is a brilliant telescope for observing the Sun, but the Zerochromat is a winner and degrade the TEC 140, sorry, but this is true. I make second test Zerochromat and TEC 140 side by side on the Sun today. Zerochromat again WINS. It has a better resolution and more stable picture and flat whole FOV. The Moon has a very low elevation now, but I test Zerochromat and TEC 140. I choose magnification 100x and both telescopes show the same picture. I set magnification 200x and I can see in TEC 140 around the crater Theophilus small blue and red atmospheric dispersion, but not in Zerochromat. Yes, it is true, you can collimate Zerochromat for atmospheric refraction!
  2. Report from a customer in Madrid:
    The night was great, we spent weeks organizing the day to be really good, we were very lucky (today is cloudy), riding it was simple, I could not help because the hands do not work well, but as you taught me in the video We did the assembly, so much was the surprise of my friends for the weight, they disassembled and mounted 3 times, because you could not believe that a person alone could move a 10 inch !, they were very surprised (I already knew it would be very easy , But it is incredible to see how easy it moves and can be mounted, great handles, very well thought out). It was easy to set-up, no problem of descolimation, incredible with the journey so long and the perfect pictures all a wonder, also the performance, left us all surprised (and I thought it was going to be wonderful !, I fell short In all the expectations, incredible great quality, wonderful creation Peter, you do not know how nice to use it has been, I have the images etched in my retinas, what a wonder), perfect resolution, no chromatic aberration, it's a wonder to use it !!, if I were not with this bump in the disease today I would have started looking to build an observatory and ask for a 15 "! I do not even want to think how wonderful it should be. We did not have acclimatization problem either, we had it in the garden and as many friends came to visit us and Noemi, we were talking while we were riding, it was a perfect experience, a great heaven (we all agreed we had a spectacular time) The moon perfect, a wonder, the focuser very easy to use (you were right!), Its use is very grateful, and it has been easy to get used to its use (as I have not used it before, it is very comfortable). And if the night was perfect, in the morning we had prepared to stay with everyone to have breakfast and to make solar observation, incredible (the whole system of filters and others brought by a friend and perfect, we were able to dock it without problem to Zerochromat, my friend already had Taken weeks ago and had prepared a small system to adapt the filter, was very stable and very easy to use). If at night the images had been perfect, on the same day, we remembered everything in what is undoubtedly the future of the telescopes, there is nothing that can compete with Zerochromat with so many qualities (they can equal in quality the great marks, but in Weight and size would be impossible), you'll see a thousand thanks Peter, I did not want to write you much that I know you do not stop working, but it was so nice to use it and enjoy watching the sky that I can not avoid sharing with you
  3. Tom Dobbins- Contributing Editor to Sky and Telescope Magazine
    The Zerochromat is strikingly handsome and finished to a high aesthetic standard. The gloss white tube with black fittings is reminiscent of the lovely Unitron and Polarex refractors of my youth. I disassembled the instrument out of curiosity and found that the design of the various components is simple but sound. Machining tolerances are impressively precise. The light weight of the OTA is a real boon, allowing the instrument to be carried quite adequately by a Celestron CGEM mount. With a 48-inch tall pier the eyepiece position is very comfortable for a seated observer. I would be remiss if I didn't mention that the instrument's fitted case is very impressive and leaves nothing to be desired. It probably surpasses in quality any coffin in which I will eventually be interred. Of course it's optical performance that really matters. In a word, the Zerochromat's color correction is superb, discernibly superior to my Meade 178mm f/9 ED doublet refractor (KF3/FK01 objective). No spurious color is visible on the lunar limb or surrounding the disc of Jupiter. Contrast and freedom from stray light are also impressive. Shadows on the lunar terminator are jet black, and features in the earthlit portion of an 8 day-old Moon are easily visible. One property of the Zerochromat design that should be emphasized is excellent thermal behavior. Thermal equilibration is very rapid and falling evening temperatures are followed with ease. This certainly can't be said of any conventional triplet apochromat of this aperture. This well-executed, novel optical design deserves a bright future and I heartily recommend Peter's handiwork without reservation. He has promptly replied to all of my questions and displayed a degree of concern with my satisfaction as a customer that is highly commendable.

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U.S Orders

CONTACT:Peter Wise BSc (Hons) FRAS
TELEPHONE +44 (0) 7990020419
ADDRESS: 5 Craig-Y-Don, Pensarn, Abergele LL22 7RL, UK
CONTACT: Steve Taylor
TELEPHONE 001 814 777 3108
ADDRESS: 2107 N Oak Ln, State College, PA 16803

The 'Zerochromat' telescope was developed by and is being marketed by Zerochromat, a British company. It is manufactured both in the United Kingdom and the USA.

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