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Hello Marco, mi sono permesso di cancellarti il numero di cellulare dal post di prima, per evitarti i problemi che di diceva Massimo…il tuo numero me lo sono già salvato…comunque se vuoi lo rimetto visibile, dimmi tu…ciao…
Hello Marco,
Yes, certainly very gladly, although for me unfortunately, from tonight, Christmas holidays end…so between work, football and various commitments I won't have much free time from tomorrow…we will agree anyway…
In the meantime, continue to ask any questions you want here in the forum, and you will see that you will find several prepared people, who will be able to answer all your doubts…
See you soon…ciao Hello Marco, see that I was right to ask…We are from the same area, and in addition we have already met, at the astronomical observatory of Nove, after the lecture by Roberto Ragazzoni…Where did you show me your work in progress of the project on’ SQM, by the way how it went on? you did tests?
In the end I also bought myself a 3D printer, even if Cartesian and not delta…P.S: I am from Pozzoleone, then a 10 min from your home…
By the way Marco,
Where are you from? what tools do you have? passions? places where you usually go to observe? visualist or astrophotographer?ah ah ah, do not worry…I'm not giving you the third degree….
it's just that I like it when a new member shows up a little, so that I can get to know him better and maybe find someone else who shares my passions or maybe coming from my areas… See you soon…ciao
Hello Marco, welcome to the Grattavetro ...
Then, as you can read in the various articles that you will find here:
https://www.grattavetro.it/category/lavorazione-specchi/tecniche/
the techniques for processing an optics for the construction of a primary mirror are various, and each has a specific purpose.To briefly answer your question I can tell you that the sequence to be used is the following:
1) it starts with the "cordata":
That allows you to quickly dig the mirror and reach a good digging depth quickly, even if the shape that is generated is not spherical. Once an excavation depth of approx 2-3 tenths of a millimeter lower than the final one, you can move on to:2) Stroke 1/3 COC:
Stroke 1/3 COC: easy easy method for the right amplitude of the past
Which is the type of pass that allows you to regularize the surface and make it become a sphere.
Once the right digging depth is reached, you can continue with the same type of pass, this time though, with cerium oxide and pitch tool, for polishing the surface.
When polishing is complete, and if the surface is beautiful spherical, you can move on to the parabolizzazione of the optics, which has the purpose of bringing the surface from spherical to parabolic. This is done with:3) Passate a W:
All the other variations of these past bases, they are used to remedy the errors that will inevitably arise during processing. But you can study these well later. For now I advise you to read carefully the articles I have suggested to you, so you can get an idea of what are the fundamental past.
P.S: obviously as we dig the mirror and we get closer to the final depth, from time to time it will be necessary to change the grain of the abrasive by gradually getting finer and finer. As soon as I find the article which suggests a sequence of abrasives to use, I point out the link, but you can also find it yourself by browsing the site.hello Mirco.
Hi guys,
I join in the even I do the good Christmas wishes to you all…
See you soon…ciaooooo Hi Massimo,
To try to avoid the problems you mentioned above, in my machine I first tried to simulate the trace of the tool center above the mirror, as the pulley diameters vary (with an Excel sheet), like this:(the difference between the two lies only in having changed the diameter of 1 of the 4 pulleys, yet the difference is obvious, the second solution is much less repetitive)
in order to find me what are the dimensions to use, to minimize the repetition of the steps on the same point. Is: if I generate a transmission relationship between piano and eccentric of 3:1 it means that each 3 turns of the table the tool trace will pass exactly over that of 3 turn first. If, on the other hand, it is possible to obtain a type ratio 3,15:1 the plan must already be fulfilled 315 turn before the track repeats.
Plus in a V-belt drive, by principle of operation, There MUST be a little slip (max 2%), which if it remains constant over time makes the transmission ratio also remain constant, but if for some reason the % slip varies, the transmission ratio also varies slightly (for this reason I prefer them over the toothed ones in this type of application).
In addition to these preliminary measures, during processing, each time vary slightly or the extension of the pass, or I hold the eccentric arm with my hand for a moment in order to slip the belt and thus change the offset between the table and the tool, or other parameters precisely to avoid the repetition of the machine as much as possible.
Well, I take back everything I've said so far…
If you look at the whole correct field tolerance in the distance between primary and secondary loooong it becomes more thrust than it seemed when they looked only axial aberrations.
Then, eye I understand that surely must keep well below the waste millimeters compared to the ideal fit, worth a rapid decrease in system performance…It seemed really strange fact, that there might be such a large margin in the longitudinal positioning tolerance of the secondary…
Ha ha ha, yes the site reminds me of something….
and there is also a nice gear motor placed right there in the foreground…I too had thought of making sure that the rotating table could be placed vertically, or have a flat mirror placed at 45 ° a couple of meters above the table so as to always leave the mirror horizontally, but then I gave up and did none of that.
But it would be really useful and convenient. Nerd, I kept focus and constant K.
I thought I'd see how the situation evolved, two mirrors data, to vary the distance between the two.
I'll show you the video of how I did, maybe I've made some nonsense without realizing.
However as you can see, varying the distance of the only coefficients of the polynomials Zerniche mirrors that change in any appreciable way are only those relating spherical aberration, while those of coma and astigmatism virtually no change.
Of course, with every change of the distance of the mirrors I must say performing this test in “best focus” because, obviously, It will move with respect to the position in an ideal position mirrors.
I will appear Giulio, I don't think anything else can be added to what you have already brilliantly said, …
you can find the little program by googling “mirror polishing simulator” or directly at the link:
http://martin-cibulski.de/atm/polishing_simulator/while here (Page 2):
I had reported a series of images of the simulations made with the program for fixed post machining, with variable overflow, and tool at 75% D. As you can see it “sweet spot” we have it with about the 15-18% the tool diameter (N:B: this applies to a tool with a diameter equal to 75% the diameter of the mirror. for other dimensions the simulations must be redone), as also suggested by Gordon's practical experience…The only note I can make on the rotating plane that I built, is to position the three support spheres of the top in a larger radius than the one at which I placed them. It will in fact be the first modification I will make as soon as I need the car again, because it happens that if you are working with a subdiameter with a lot of overflow, the center of gravity of the tool can fall outside the radius of the support spheres, causing the mirror to overturn, floor and everything on top of it…
Interesting….
However, playing a little’ with ATMOS, using data from your optical configuration, I saw that (with ideal mirrors, then optically perfect) to introduce spherical aberration of lambda / 4 to the optical system, We must dismiss or allow the mirrors of about 3.5mm while the lambda / 2 aberration that amount rises to +- 6.5mm…
Which it is a great margin.So I am feeling thought that the tolerance in the distance between primary and secondary was moooolto more thrust, as I see it is not so. Also to get used to a bit 'of numbers, if you fail the installation of mirrors and mounts them 1 mm closer or further away, It is introduced into the optical system spherical aberration equal to lambda / 13.5. In short, quite small in relation to the value of 1 mm that already consider a wide margin and easily improvable also at amateur level or in any case non-professional.
I do not know yet instead evaluate, that could affect the final yield a decentring of the secondary.
Hello Franco, the greenish glass is fine, It is the common float glass….
There is also the clear (transparent) which is obtained thanks to a particular process that is able to almost completely remove the iron oxide which is present in the float greenish (and that is precisely responsible for the color). I only do it for a matter of design or design but for our purposes is fine greenish (it also costs less)…
