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In my opinion, the problems you encounter are largely related to the use of non-uniform temperature in processing:
Other things to remember are the adaptation of the tool may well be done even when it is lukewarm to speed up the acquisition of the mirror shape a little, but then during processing it will only be the friction that uniforms the temperature of everything you use.
It is also always necessary to cut off the protrusions of the pitch from the tool disc. Certain non-tool and mirror scratches come from their uncontrolled crumbs.
Then you must not weigh with your hands on the tool otherwise the crushing produces a premature occlusion of the canals, and also protrusion of squares beyond the tool circumference.
a tool must last until the end of the parabolization, because doing it again changes the way you work, when the final tolerances have become a few millionths of mmA pitch that can be judged empirically right, releases the conifer scent after about half an hour of work, and requires reopening the grooves with the tip of a soldering iron, only after several hours of work.
On hot water for polishing, it should be borne in mind that its localized use raises the glass molecules. And that's what makes the tool smooth without friction, since it would only rest on a fraction of the surface (John Dobson also points out in his video).
Hot water can therefore be a useful expedient to abrade more in the "heated" area, but in the long run it is dangerous because it artificially changes the shape of the mirror with different temperatures, although obviously very little due to the poor removal that the oxide used produces, but the tolerances are of the same order of magnitude.
When polishing by hand, it is recommended to use cerium oxide, not to add the powder because it infuses an absolutely irregular amount, changing the contact surface and ruining the fit in one fell swoop.
Is’ better brush it in a creamy state, occasionally on the tool or mirror, diluted in a container with the ratio of one level spoonful of oxide, with two or at most three tablespoons of water.
In theory it would be almost useless to add cerium oxide during processing, because what works is only what is encrusted on the surface of the pitch squares. The rest is lost by leaching without working.Long "pulling" a nuisance trusting in normal friction, you get to have a lot of resistance to movement, conifer scent and whistles, which indicate that the time has come to avoid inducing inadvertent pressure on the tool. The discs are then separated, the surfaces are cleaned with a sponge, the oxide is brushed, and we start again with a new annoyance.
This is what I remember being the most decisive in the progress of the polishing work.
As for the plaster for the tool, the friend Andrea registered here “Beta Capricorn”, who has a lot of experience on the subject, he suggested me in this same Forum (but I couldn't find the discussion, because I don't know how to search) not to use very hard plasters to be cast directly on the mirror, because they reach a hardening temperature proportionally high to the final hardness, which therefore exceeds by a few dozen 100 degrees, with the risk of breaking the mirror.
However, there is a type of gypsum suitable for a certain specific dental application (…which is in that discussion that I would like to find again) which is much harder than normal plaster, but has a hardening temperature lower than i 100 degrees.
(IF you could find that post, thank you if you suggest it to me)
Giuliothe last one I threaded it like a ring gear and I put a stainless steel threaded bar on it!! the last one I threaded it like a ring gear and I put a stainless steel threaded bar on it (the last one I threaded it like a ring gear and I put a stainless steel threaded bar on it) the last one I threaded it like a ring gear and I put a stainless steel threaded bar on it “the last one I threaded it like a ring gear and I put a stainless steel threaded bar on it”, the last one I threaded it like a ring gear and I put a stainless steel threaded bar on it. the last one I threaded it like a ring gear and I put a stainless steel threaded bar on it “G” to have the turner make the first pieces for the maintenance of the steel tube rolling rolls.
to have the turner make the first pieces for the maintenance of the steel tube rolling rolls, to have the turner make the first pieces for the maintenance of the steel tube rolling rolls “to have the turner make the first pieces for the maintenance of the steel tube rolling rolls”, to have the turner make the first pieces for the maintenance of the steel tube rolling rolls (to have the turner make the first pieces for the maintenance of the steel tube rolling rolls), to have the turner make the first pieces for the maintenance of the steel tube rolling rolls, to have the turner make the first pieces for the maintenance of the steel tube rolling rolls (I think), to have the turner make the first pieces for the maintenance of the steel tube rolling rolls.
to have the turner make the first pieces for the maintenance of the steel tube rolling rolls, to have the turner make the first pieces for the maintenance of the steel tube rolling rolls…. to have the turner make the first pieces for the maintenance of the steel tube rolling rolls.
Nice memories.Nice job Massimo!
John Dobson's survatura and astigmatism verification system is excellent!!
Thanks Massimo!
I will read with pleasure. (Even if I am in the Newtonian constructive mechanics in which I lean, I'm very “Spannometrico”).
Welcome Massimo. My present.... My present....
(The yellow colored material that you used for the transmission of motion to the metal wheels, The yellow colored material that you used for the transmission of motion to the metal wheels? The yellow colored material that you used for the transmission of motion to the metal wheels, The yellow colored material that you used for the transmission of motion to the metal wheels?).
The yellow colored material that you used for the transmission of motion to the metal wheels.
GiulioHello geminimac.
Your questions that I read are a classic doubts of those who are about to polishing.I suggest you read the article tutorial that this site contains answers
This is because to answer here in full, I should bring back the entire content, starting with cerium oxide dilution.
About the tool instead of the grooves; Do not worry of their form. What matters it is the contact surface.
You will also read this, when you chipping a picture.
The grooves you must always restore them without problems, for example in your case with a soldering iron.
This is because when the melting of the pitch quedretti bound them together at the base (or when the tool is made by melting the surface in a single pitch, obtaining the grooves per impression with a plastic mesh) if you used a knife and a swing to blow up the pitch (how do you usually on the individual squares) since the pitch-jumps with ease, It would run the risk of breaking many adjacent squares ruining the tool in a too extensive manner.
And for the successful completion of the work without astigmatism, It is always recommended having to redo the tool in the course of work, starting from the guessing the hardness of the pitch that will not be too hard (and create errors area for its excessive deformability); or vice versa too soft to limp tapering too quickly.
Normality is able to arrive at the end of parabolizzazione with a minimum thickness of the squares of 2 o 3mm, which favors the best shape of the surface, when at that moment you find yourself having to deal with very few nanometers that make the difference of optical quality.Notions I read, used and remembered even in the preceding articles that indicated.
Ciao. good job
hello Geminimac
I understand your qualities of perseverance in the fervid imagination, I see confirmed, as well as by way of scratching with sandpaper instead properly with abrasive powder (creating multifocal astigmatism and furrows impossible to eliminate, Instead of the easiest point craters left by the dust), also on the type, shape and unusual characteristics of too small squaring; too shallow depth of the grooves unmaintainable open in processing; too small asymmetry of the tool grid into pitch you've accomplished.Yours are precious qualities that you can use profitably to invent other new ways, only taking as a guide the complete knowledge of the reasons that regulate the "old street" optimal realization of mirrors for telescopes. Street super-proven for more than a century of history astrofila, where technology has remained and still remains manual.
Only with the knowledge and respect of the many reasons that determine those “stakes”idispensabili, you face the chance of new experiments potentially ameliorative.
All that said, , potendoti not advise otherwise without quoting whole chapters of notions that are part of the old road, My advice is to get the 5 fundamental chapters: two for the "scratching of the glass” (chapters 2 - 2bis); and three for the design of a Cassegrain telescope Coude (chapters 6 – 7 – 8) with scalable measures to any diameter, because proportional to the diameter of the primary mirror.
They are fundamental chapters, with illustrations of the book by Jean Texereau, available for free download from this site: http://www.astrosurf.com/texereau/
Chapters that if you do not know French, You could translate into Italian using "Google Translation", choosing the language French origin, to be translated in the Italian, and then clicking on "Document", to indicate one at a time PDF chapters downloaded in French.
Launching the translation will have the translated text on the screen that you can save and print, But looking at the many figures on the original PDF.
Good job in the cell Massimo!
The grit 80 It makes its way in a hurry, and processing in the robust cell is the solution that comes to mind first.When the meniscus, I would say that in any mechanical disc of any printed material or limp to “bowl” mentenendo the same original uniform thickness, stiffens.
There is always time to do experiments on the substrate.
Experiments that would see well only to verify if done with mass material inifinitesima and equal coefficient of expansion, It may prove to be somewhat equivalent to the mechanical construction of more technological cell. And then check if its construction is not “difficult”, according to “mission” and the thought of John Dobson tended to combine simplicity with functionality, and then be extended to these difficult optics.Hi guys
The solution to realize reflective mirrors with a meniscus of commercial glass thickness 20mm, for its softening and sagging on a curved surface, solves the problem of large excavation that would be necessary in the glass. But then on the meniscus need to work polishing and parabolizzazione, and then serve a support able to bring the flat rear surface of the meniscus curve, possibly, if combined with the mirror glass, that is, without inducing therein the constraints that generate higher deformations to 68,75 nanometers high., dates from different coefficient of thermal expansion.I find myself accustomed to the practice of brainstorming, and I read some time building insulation FOAMGLASS, albeit in reference to uses different from those optical…because from experience, poprio in remote areas have often found the neighbors problems solutions.
I had seen on YouTube videos that the brick structure of the closed alveoli FOAMGLASS, It makes shearable freehand with a wooden ripsaw, and then I imagine that it can not be difficult to be machined to achieve the concave support excavation for a meniscus (… with classical abrasion, or milling, or other).
The mechanical-thermal validity of the support for the machining of parabolizzazione (or as rear face coupled to the mirror) I think it would good for lightness, strength, absence of elasticity, and thermal expansion equal to that of glass.
The specific weight of 100kg per cubic meter is FOAMGLASS, that is 26 times less than normal glass which is of 2600kg per cubic meter.I also think that one of the problems could possibly be the type of “glue” to join the meniscus to the rear base support, so probably respectful of optical tolerances.
And here I would find interesting to try with the usual pitch, which it is always a mechanical interface for machining of optical lenses, with it fixed on the supports of figuration / polishing machines.
The pitch is a parent of carbon fiber in large quantities, and therefore also has very low expansion; and as the glass is a ritenibile “liquid” solid at room temperature (it is instructive to know the following experiment of its “slow speed” sliding caused by simple gravity https://it.wikipedia.org/wiki/Esperimento_…_goccia_di_pece)Besides, there are around glued working doublets with pitch for centuries, that if conditioning between two surfaces, by capillarity keeps almost forever its bearing characteristics not coercive.
The implementation will be interesting and not easy. But beyond the chatter of my, in my opinion (it is not a contract, but a trial) agree to take the simplest ways that there will be in the street mind facendo..come realize the plaster support such, because there is always time to correct errors as they arise, without “fasciarci head until it has been broken”.
Thanks Frank_q.
A voice for their trials like yours, in a cutting-edge technology such as 3D printing, on a critical suggestions on the little-known technology that involves the post-print behavior
of materials related to the melting wires usable, It is always desired and appreciated!! Just being able to "not original".
For professional experience of mechanical design requiring intense “brain storming” between the technical experts, I would rincuorarti not to feel depressed for not being original state, why in the world, even without our knowledge, everything has already been invented by others, at least in the functional principle; at most and only modern technology, Unknown once, can change something for the better.
Often a seemingly unique solution, It is no longer such deepening the study or discovering that already exists in some kind of technical use. If, however, also an undesired micron movement becomes adjustable and deleterio..allora problems and costs rise dramatically.All that said, , if there are, should look for workable compromises, for example, if it does not consist in a limitation not being able to reverse the motion, it is easier to obtain the absence of back-lash being able to pre load in reverse motion an axis (even just with the example of the telescope tube weight) saving in constructional complication.
A pleasantly beautiful activities is definitely the design in itself, especially if you have no time deadlines.
hello ConCalmaFaccio.
doing local mind on the type of telescope that Newton would build to use it even in astrofotohgrafia. you step a few links that you can afford to shed light on possible design features at the level of DIY.On the issue of full frames of construction, Newton and Cassegrain telescopes, starting from the creation of the mirrors, the FREE text, certainly some’ dated but for its fundamental nature and conceptually timeless clarity… is “the Bible” in the field, and is the French book by Jean Texereau “The construction of the telescope amateurs 2nd edition that has now pdf, downloadable chapters or whole
http://www.astrosurf.com/texereau/Since the Newton to make photography has an important dimension, and the best frame constructible amateur (course in my personal opinion) I venture which is that “Horseshoe” like this:
https://www.webastro.net/applications/core/interface/imageproxy/imageproxy.php?img=http://www.astrosurf.com/zeubeu/T500/IMG_20150705_102529_bis.jpg&key=81b9063bcf422a0586282feb8676fc7a21eda6615d468edaa6462962f40aaff6Is’ designed to accommodate a 500mm diameter Newton, but for the moment it is not shown the anchoring of the tube 500, but it is shown with a board supporting a dobson diameter 300mm
…We therefore suggest you take a look at the coming discussion of project that image, which is at the following link:
https://www.webastro.net/forums/topic/132038-construction-dun-t500-et-de-sa-monture/?page=7As for your point 1, REFERENCE TEXTS: From the point of view of the optical link that gave you Mirco is part of a very extensive and thorough directory of optical astronomical topics.
3D PRINTING:
Given that I know very little about the 3D Printing, but I have some knowledge on plastics; They are led to consider the PLA not reliable nor lasting mechanically. It would be much better Nylon 66 or polyethylene. I doubt, however, that the type of printer suitable for these wires is available at costs practicable for the hobby.
Even our writing has experimentally tested the feasibility of printing a Foucault tester, which, however, was not satisfied. then I see the press 3d relegated to a rather marginal use.As for the CAD, if you do not have it yet, I suggest you take a look at what nEach much use, that neither DOUBLE CAD – TURBOCAD LTE5 . It is a free open source and quite similar to the profile Autocad, opening and saving well in DWG. The use of infrequently, It is non-invasive and runs fine on Lap top HP is not recent, that purchase used and reconditioned with guarantee at “Simpaticotech”, preferring “old” senior HP machines and much-performing, purchasable among the 200 and 300 euro, ex leasing industriali, placed in position and secured.
Ciao.
If you have to insert mages you have to first upload them to a free host computer,(for example http://www.postimage.org) which in turn will give you some choices link with some link, among them you choose one for insertion of the image in a forum.
You paste into the address that your answer.
I believe that, Your dealing with a particular project, some image is essential to understand what it is.Technically, for example, one of only three ways to reduce the height of the Newton (at the cost of greater obstruction) It is to postpone downward the optical axis cone with a flat mirror inserted along its path, then to divert it with a tertiary elliptical outgoing floor next to the primary (kind “fire Nasmith”).
Ciao. Welcome.
You've read, but frankly I have not figured out how to make that intenderesti compact Newton.You can make a sketch?
What I know, is that a plane mirror, even more if large diameter, It is very difficult to achieve, because it needs three tools of the same diameter, working with all three with alternations indicated by the spercie “truth table” type of computer, and using an interferometer as a guide.
If you will understand truly realize the large diameter plane, Your will certainly be a departure “uphill”.
On my return I could still make it in writing a tutorial article on that work.
I await your thoughts.
Ciao
Giulio 8
