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Again Hello everyone
I decided to write here because I was not sure what section to ask the question (I do not know if it is the right forum), but someone has information regarding multiple mirrors? On the net I found that great and maybe some of you can help me!”
Hello Marco. the only telescope “multiple mirrors” which it is within the reach of an amateur, is the Binoscopio, that contrary to binocular turret (that divides the luminous flux of a mirror to provide light to each eye half), It is able to provide each eye of an entire mirror light, actually doubling the lrestazioni.
But I think you riferissi the mirrors consisting of elements that are a fraction of the opening made by the whole…because a telescope to operate must be able to rely on a unique rilettente machined surface consistent with the type of the telescope configuration (that parable, hyperbole etc.).The composite construction is virtually impossible at the amateur level.
You can not work only one part of the parable because you could never make it work visually with the other parties, if not using a correction system with adaptive optics automagic (justified as that of large telescopes), which is outside the scope amatofiale.Hello Marco, I moved the discussion in “Chalkboard grattavetro”, the space dedicated to all questions, curiosity and anything else that may be not included in other sections of interest.
I did not understand what you mean by “multiple mirrors”, if you are referring to a combination of more optical or to a primary achieved with more small components ( ad is.: Honeycomb ) to achieve a large final diameter, like the James Webb Space Telescope, or even the E-ELT ( primary 39 meters realized with 798 hexagonal mirrors !!! ) they are building in Chile:
actually I explained evil, I do not speak of telescopes multi mirrors, but of telescopes that have mosaic mirrors as with that of Chile. Their aim is to lighten the structure (because the plates are very thin) and consequently limit any vibration resulting from the movement. What they failed to understand is if the hexagonal plates are flat or curved or, even, They are flat but so thin as to be curved from the support.
In ESO documentation it states that the felescopio consists 798 esagomali segments from 140cm in diameter, each 5cm thick for a diameter of the full speccho 39 meters. I have not yet found, however, information about the type of work each segmaento.
A technical article specifies the way of processing of the individual hexagons by means of a sophisticated numerical control machine on three axes, able to work every segmaento the large parabola overall in a short time and without damage to the substrate vetro.Ma leaves a surface roughness with a little more than 1 microns. It is not specified the use of that machine for polishing and the parabola correction, bringing the precision and roughness of the surface inside the famous 68,75 maximum nanometers of a lambda / 4
Everything this, na especially tolerance 68.75 nanometers high., exclude the’ Use of floors segments, and also their local deformation impossible for each different fragment of parable, He admitted that the possibility would be unstable, inaccurate and thus unnecessarily expensive.
.A 3-axis ultra precision free-form grinder is under development at Cranfield University. The machine will generate large optics with high form accuracy, at high material removal rates and with low sub surface damage. In this paper the basic machine structure and machine motions are introduced. The choice of geometry of grinding wheel is discussed based on the analysis of wheel/workpiece contact. The focus is on the “r, theta and Z” grinding mode. Two algorithms are proposed to deal with changes of contact points and Non Uniform Rational B-Splines (NURBS) interpolation in the grinding mode. The machine will eventually provide a rapid and economic solution for grinding large off-axis aspherical and free-form optical components for industry.
Grinding mode of the “BOX” ultra precision free-form grinder (PDF Download Available). Available from: https://www.researchgate.net/publication/264847981_Grinding_mode_of_the_BOX_ultra_precision_free-form_grinder [accessed Jul 15, 2017].
Here is the entire project : https://www.eso.org/sci/facilities/eelt/docs/e-elt_constrproposal.pdf
work progress
: In May 2017 the fusion of the secondary mirror is finished having a diameter of 4,2 meters and weighing 3,5 tons. The raw glass was produced by melting the glass ceramic Zerodur, and at the time of creating the largest ever implemented secondary mirror for a telescope and the largest convex mirror ever produced so farthe report ( robe yes “extreme engineers” as Mirco, I like my usual I only read the figures
) it is seen that the mirrors are actually 5 
( 2 are plans ) for a fire Coudé / Nasmyth in F17, namely a focal ( oltreuttto variable ) of 663 meters ! if I put my eye to 15 I could look in millimeters 44000 magnifications 
Hi everyone,
I saw only now this thread…
no Marco, amateur is absolutely impossible to build a telescope mirrors that multiple functions (specific functions that, because it does not work you can very well…ah ah ah.. ).
The machining tolerances, both of radius of curvature, both conical constant are too thrusts for an amateur builder, not to mention the tight tolerances of positioning of the mirrors, to ensure that are able to work in unison.
If you can affect I suggest this article, in which they are shown different machining tolerances for the GMT (Giant Magellan Telescope, 24 meters in diameter!!!):
http://www.gmto.org/Resources/GMT_5494-8.pdfMaximum: sooooo nice that document on’ E-ELT, I had not yet read.
However, both the E-ELT primary is formed by a whole series of hexagons every one worked so as to form at the end of a single ellipsoid with K =-0.996. So I'm quite contoured, every one, with its own specific form of dressed ellipsoid, are no plans. Then there are other 4 mirrors, of which a secondary and a tertiary conical, to eliminate most of the optical aberrations, a quarter mirror plane on which intervenes adaptive optics and a fifth that sends toward the fire Nasmyth the optical beam.
Another impressive thing is that the primary has an F # = 0.93, which results in a primary arrow over 2.5 meters!!!!!!!!!!!!! Not to mention the size, of rocks in play, of the wind relative forces produced by such a large dome, and the fact that it will be built in a very seismic zone… Sorry, l’ topic is very interesting.
Guido Horn D’ Arturo created the first mirror mosaic years 30/ 40 (if I'm not wrong) and you can see in Bologna.
This has a metal support on which the dowels are positioned. The’ whole outlook, in a newer version, He was subsequently processed, with the plugs already positioned. Because of the problems due to the mechanical and weight l’ optical works only in the zenith, but it works.hello Luigi.
The multiple mirrors, are substantially “easy” to be built only to realize telescopes too long focal length to be able to be positioned differently than aimed at the zenith.The reason is that a mirror to bring into a single focus the light rays captured by its extended surface, must be parabolic, ie presenting a reflective surface with a curvature continuously variable as is that of the parabola, proceeding from the center towards the periphery.
This presupposes the enormous difficulty that each component block the mirror is done in a different way from other.Quell'ostacolo of difficulty can be overcome with the use of modern machines (see Webb Space Telescope) not within the reach of the amateur, and sophisticated systems for collimating and collimation “to have an agreement” the reflection of all the plugs; Or that obstacle can be circumvented by creating a co telescope a large focal length, to ensure that the deformation is expected to have the parable, It is so minimal as to be confused with the curvature of a sphere, who famously radius owns one, always the same from the center to the edge mirror, for all blocks.
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