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A new visual telescope concept

I am a self-builder, visualist amateur astronomer. I decided to try to make the perfect telescope, which obviously does not exist, but for my needs it is well defined and whose research has led me on a road outside the maps .... Too often, materials such as glass or carbon fiber, aluminum, plastic have been used; it is believed that robustness is a prerogative only of these materials. Obviously this is not the case at all. These are elements whose production, processing and disposal at an environmental level is extremely complex and energy-intensive, which is why their use in the opinion of the writer should be limited to situations where there are no alternatives. I have thought for a long time on what are the constraints in the movement of the instrumentation, that is the movement in height and the movement in Azimuth (referred to the altazimuth). In fact, in this solution the manual movement of the instrument is very easy when pointing an object far from the azimuth axis, therefore towards the horizon. As one approaches the zenith, it is necessary to act simultaneously on both axes with reduced handling due to the reduced angular distance of the two axes. The result is a more problematic movement, to the point that the area surrounding the zenith is somewhat universally considered "a dead point".

Too bad that this area of ​​the sky is the one that allows the best transparency...

Among the characteristics of the wood there is that of being composed of aligned fibers which when superimposed in crossed layers (as in the case of plywood) can guarantee a very remarkable seal. I proceeded with the gluing of curved pieces on special templates and this made it possible to bind the various layers, strengthening the entire structure, and, with the internal tensions of the fibers themselves, the result was extremely high strength combined with considerable lightness.

For this reason, I have decided to develop a new project, which I have called The Spherae Program The Spherae program is more than a project, as it does not refer to a specific model, but was created to fill the chronic gap in the sector of tools dedicated to pure visual use. The already mentioned "dead area", that is the zone of about 30 degrees around the zenith, represents a weak point for the altazimuth instruments. Another critical point is represented by the sliding in height. The declination circles are too large and cumbersome. Finally, the sliding of these takes place on 2 points per side, therefore on four points. The dips over time lead to some hopping when pointing the instrument in certain areas of the sky. The question I asked myself was:

is it possible to make an instrument that slides on three points of support? If so, is it possible to move it on one axis only?

The answer is yes.

Those that follow are freehand sketches.

I had some "morning lightning" when I woke up, and I brought them back to paper in the best possible way. I'm not a technical designer, but I think they convey the idea sufficiently.

English: Testo

As in the Astroscan model, taken from several amateur models made in the mid-1970s, in which a sphere rotates on three points, here we reverse the concept: three points that rotate inside a sphere. The sphere is a ring. The three points are six circles. The scrolling circles in height, which in a traditional Dobsonian are external, are here an integral part of the cradle of the primary.

English: Immagine

The structure is open: this allows a quick acclimatization of the mirror, an easy collimation, a practical and versatile balancing. The curvature of the cradle must be similar to a sphere. A closing ring in the upper part guarantees a high sturdiness guaranteeing an absolute non-deformability to the cradle.

English: Immagine

The cell of the primary mirror is therefore anchored to the three arms of the cradle, placed at 120 °, The cradle rotates within a base ring. A series of removable counterweights allows a correct balance of the optical tube cover. The collimation knobs themselves act as counterweights.

English: Immagine

The primary cell is a single body with the sliding arms of the cradle. This is made with seasoned hardwoods (I mainly use walnut and ash wood)

The layered construction allows for remarkable strength and lightness. The processing is carried out with a router and by hand. It is not a quick or easy job, the tolerances are very small.

English: Immagine

The optical tube allows a complete and continuous rotation on its axis, this allows a great comfort of observation at any height on the horizon. With diameters of 50 cm with focal lengths of about 2 meters, the eyepiece aiming at the zenith is about 1.74 cm high. For shorter heights above the horizon it is possible to rotate the instrument to adapt the position of the eyepiece; this is possible by acting on the secondary ring, like on a steering wheel. Note from the images that the laser collimator confirms the absolute rigidity of the structure: during this operation the optics remain aligned.

English: Immagine

To allow this rotation, the truss tube system must have absolute rigidity; this is unfortunately impossible with the classic Dobsonian anchoring systems. To make a solid and precise connection, I made some threaded rods at the ends. So are the hooks on the cradle and on the secondary ring. Assembly is fast and accurate. Bound

English: Immagine


The structure has a distinctly minimalist style: in the course of development I have eliminated any component that is not strictly necessary. When the instrument is mounted, you are not faced with the classic solid Dobsonian, but a thin, almost "transparent" instrument.

All the components that characterize a classic altazimuth, therefore rocker box, basic sliding table, sliding rings in height, primary cradle, are normally very evident. In this case they are all integrated in the primary's cradle.

But there is one ... the machining tolerances, which are normally distributed over several elements, in a minimalist tool like this are all "concentrated" on a few elements. Here the sliding arms of the cradle, with the closing ring and the base ring, have an extremely complex processing. It took me 4 years to perfect these pieces.

I say this very sincerely: the processing of these components is more difficult than the optics.

I am available to make this type of instrument on commission. For the moment only the 50cm diameter version is available, but soon there will also be a 60cm version.

For information contact me via whatsapp at +41766136028.

English: Immagine

All images and texts on this site are the property of Ruffini Luigi.

Copying and reproduction of the same without authorization is prohibited.

English: Citazione
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