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hi Luca,
Difficult to say for sure what the problem is.
From what you say it seems a problem of pitch adaptation or of the fact that you cannot always keep the adaptation constant between the various sessions.
I can tell you that in my experience I have never heated the tool before processing, apart from when I wanted to adapt the pitch very well, but then I let it cool off before starting the work session (much later 10 min of work the friction due to rubbing, it warms up just enough the surface of the pitch to make it yield and perfect its adaptation, which must have been more than good at the beginning though).
Else, I have never used hot water for cerium. I don't want that when you add it, if this is not distributed immediately evenly, you can find yourself with mirror areas and peace warmer than others.
What I've always tried to do, is to maintain a stable situation as much as possible, also thermal, between the various parts (mirror, tool, cerio, water etc.) and to do this I left all the parts in the same room so that they all had the same temperature at the beginning of the session.
At the moment I can't suggest you anything else.
It could help if you can post some pictures of the tool and Ronchi.
Hello and see you soon
MircoHi Massimo
welcome here on the forum also from me. Congratulations on your realization
I am curious to read the various solutions you have adopted for the construction of your telescope.
Ciao
Mircohi Luca,
Eeeee had happened to me. Look before you re-melt the pitch, try imnergela in hot water, as well softens a bit and you can try again to make the adaptation.
Anoint well as the network with the oil. hi Luca,
Glad to reread
I think the disc 10mm aluminum as support, will be fine, although I could not tell for sure if it is adequately drive. I have always found it very well or with marble discs (I cut them a neighbor, cost content but are very heavy) or with the dentist from plaster-plates, very cheap, beautiful rigid and lighter. I think the ideal solution.
To pitch, anchio at the time I had done a lot of evidence, it is not easy to find the right mix. But given his work, I would say that Max was able to find good mix, and the suggestion that you gave is great. Or if you prefer ready for use, Just buy the Gugolz.
Hello and see you soon
Mirco It Massimo Gui plop, probably it has limitations.
Look, while I would try to put a long loooong focal, in such a way as to simulate a virtually constant thickness blank, as has incidentally your meniscus.Hi Massimo,
Ohhh great, I see that the work is progressing
We say that not surprise me at all that the meniscus is not curved so smoothly during the softening in the oven. It happened to me too, when I tried to make the blank lightweight, you see:https://www.grattavetro.it/forums/topic/primario-420mm-foca/page/2/
In any case, returning to the question deformations, we say that does not change much from a disc or a meniscus curved, and this is due primarily to the fact that the curvature of which we are talking about is not so accentuated. I can also tell you that in the first approximation the cell that generates you Gui Plop, You can be considered valid also for your mirror meniscus.
That said you consiglerei to try to generate two types of cells, An A 18 points and a 27. Then just I have a moment, I try to make the most precise calculations, using these cells, inclinations to Vaie.But as for the cell you're using now, during processing, and, I would definitely recommend to realize a much more robust, aluminum or steel.
Hello and see you soon
Mirco Oooooh Very Massimo
As far as I can see, This time you decided to embark on a more ambitious project that
I can not wait to follow step by step progress, and see how you can solve, the inevitable problems that will crop up with a project of this size.
See you soon and good work!!!hello Fabio,
Absolutely recommended the text you indicated you Giulio
Aaah well, then we are colleagues, I also have mechanical engineer
The 3D printer I have it at home anchio, I paid 200 € (to assemble) and use it regularly and there around the mold. I think it's one of the most well-chosen purchases I've ever made!!!
The PLA is easy to press and has a good mechanical resistance, However, as soon as salts with the temperature it tends to sag. To give you an example I had printed a cell door to put on the handlebars, GPS tracking to keep me in the hand, for the laps that I did. Well, remaining exposed to the sun, It is afflociato under its own weight (not to leak for charity, but she has lost its original form). So the PLA is easy to print, I often use, even for parts of my telescope, but it has its limitations.
The’ ABS moooooolto better resists to high temperatures, It has a good mechanical and abrasion reistenza, but it is much more difficult to be printed, They need higher temperatures, both the nozzle of both the plate and tends to detach more easily from the printing plate, making ears or worse, to the workpiece under construction.
However almost all printers are capable of printing these materials, others could not tell you.
Hello and see you soon
MircoHello and welcome on my part
Always nice to read that someone wants to try to embark on the road dell'autocostruzione!!!!
The project you propose is certainly not without difficulties, both for collimation problems he alluded Massimo, both, as you already said Massimo and Giulio, because of the difficulty in achieving a plane mirror which is very high. Difficulties which obviously increases exponentially with the increase of the diameter (as demonstrated by the prices of the secondary elliptical plans).
Realize then a mirror plane of 175 mm diametro, I see it difficult, as well as the necessary manual skills (but this certainly does not scare, otherwise no one never start anything), but especially for the equipment needed to test, first of all the need for a mirror of diameter at least equal floor, already optically floor, to use as a reference.Beyond all the difficulties listed above, that in some way you can deal with and more or less overcome, ti discouraged to embark on the construction of the optical configuration as well as you thought, not so much for the realization difficulties, but because it is a configuration with optical performance NON acceptable (especially if you want to do photography).
The motivation lies mainly on the value central obstruction due to secondary mirror plane. Value which in your case is 50%.
The central obstruction produces a decrease in the contrast in general, Not that a decrease of the Strehl value. The introduction of a central obstruction also, It induces a negative effect similar to that produced by spherical.I carry this link where you explained everything very well (Also the two previous pages in this):
https://www.telescope-optics.net/telescope_central_obstruction.htm
Beyond the whole explanation, which it is quite complex, to synthesize the issue, you just look at the first graph in the upper left of the linked page. Again the question is more complex, But beforehand you can see how already perfect perspective, the maximum acceptable obstruction, not to fall below the 0.8 The Strehl, he was born in 32-35 % circa. If then it is obvious how the optics at your disposal has a Strehl below 1, the maximum central obstruction decreases to values that are much lower, of the 50% the optical configuration you proposed.
This does not imply that you can not categorically make the optical configuration that you have proposed, but only that doing so, performance resulting nullify all the efforts made for the realization.For these reasons, I would recommend you evaluate other optical configurations.
Hello and see you soon,
Mirco ciaooo Louis, A warm welcome also from me…
I see that you are already in the advanced stage of the work, I follow with interest that your project…nice time…
See you soon…ciao… Hi Stefano…
the progress Congratulations…
you see that you have taken us out and that you are very safe when handling…I see myself in this video…
It will follow with interest future developments…good job…ciaoHello Marco,
I assure you it is so, I am not only based on my experience but obviously also on technical data and theory.
In the image that I have attached below, viscosity curves are shown, depending on the temperature, of various types of glass.https://www.grattavetro.it/wp-content/uploads/2017/08/Curva-viscosità-vetri.png
As you can see from the curves I highlighted in bold, the one in "black", which represents sodium calcium, it is much lower than that of the "blue" of borosilicate, which indicates that calcium sodium softens sooner.
Indeed, in accordance with the experience made, at 1075 ° C the calcium sodium has a certain viscosity (which allowed me to fill the mold well) while to have the same viscosity with borosilicate I would have had to rise to at least 1300 ° C.
Furthermore, always at 1075 ° C the calcium sodium has a viscosity of approx 2,7, while borosilicate of approx 4. Since the scale is logarithmic (base ten) means that at that temperature the borosilicate is 20 times more viscous than calcium sodium, and this explains why in the prva that I did with borosilicate, the various scales did not melt well, but only softened and stuck together. See you soon, ciaooo…
Hello Marco, yes that article I remember reading it…interesting…
anyway, building a good oven is far from easy, maybe not so much for the maximum temperature that can be reached, but for the quality in the’ thermal insulation, since for your purpose you need a very slow cooling…
I do not remember well, be yourself, you just want to attach the glass for softening or if you really want to melt it, but if your intention is to try your hand at pure glass fusion, 1000° C are few.
in all the tests I did I always managed to reach the actual 1075 ° C, and they always seemed few. Then it also depends a lot on the holding time at this melt temperature. I have never gone beyond 3-4 hours of maintenance for fear of ruining the oven.
However, be careful that borosilicate softens at a much higher temperature than calcium sodium (and not lower).
That time I tried to melt borosilicate, the 1100 ° C reached by the oven were not even remotely enough to melt the glass flakes. They are all just softened, sag and stick together, but it was not. The final appearance of the blank looked like that of polystyrene…
While using the same oven and the same maximum temperature, the calcium sodium has melted very well, apart from having it all cracked in cooling, but that's another problem (not to mention the air bubbles that are trapped, differential expansion between mold and glass, etc…
)
