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Look,today browsing the net I found an online glassware from which you can order the disc of the diameter and thickness you want, the finishes you prefer and already tells you the total to add to the cart. The price is not very low but not exaggerated considering shipping etc.. Two discs as I wanted to get me 126 + VAT. Clearly without rounded edges (I'll smooth them out myself) otherwise the price goes up a lot.
Incredible… I can't find a glass factory that gives me a quote. I sent 3 mail and phoned others 2. In two others I went in person. I ask for the same things, two discs of 305 mm monolithic glass, thickness 19 mm. In those where I went in person, names and surnames and emails were noted and they should have given me a quote in a couple of days. Nothing.
In those to which I have sent emails they have not even answered me. Of those I phoned one told me “Eh, they will be on 120 the one + vat and I could get them to him by mid-August” Ehhhhhh?! 120 + VAT? Mid-August?
The other one I called told me that she doesn't know how to cut the glass from round 19 mm… works “I'll cut it into pieces but it might not turn out perfect…” A glass factory… he doesn't know how to cut a glass disc… ah ok, it doesn't matter. But am I unlucky or what? Glass, very common non-tempered glass, calcium-sodium glass… I keep looking
Thanks Giuseppe, the challenges are beautiful for that… The obstacle presents itself, we study how to deal with it, you pass it and rejoice… It is not surpassed? Try again.
In the end I opted for a 300mm f / 5. I'm waiting to call the glass factory to tell me the total and then give him the green light or not. I asked for two 305mm discs with 19mm thickness, of non-tempered calcium-sodium glass.
Now then I'll open a separate thread since this is the section for presentations. However, my concept would consist of a Dobsonian with a full aluminum structure, designed with Solidworks and machined with cnc. For the tubes I would like to use carbon. I will think a little’ what to do!I had enjoyed reading your article on acclimatization tests and on the fact that a thinner glass, provided it is supported by a well-made cell, it follows better the thermal excursions etc but I thought that a glass of superior quality, when taken in similar thicknesses, was superior in performance. For example a Supramax with thickness 20 mm and a calcium sodium with thickness 19 mm will have differences while maintaining a similar acclimatization curve… but I do not understand and I could say cialtronate.
On Stellafane I saw various techniques for the creation of ceramic tools, metallic and various alternatives but I see the glass tool more convenient for observing the contact points, for example (I know there are so many methods), for testing and more. Clearly, if you go to certain glasses, the use of a twin tool is out of the question, it would border on blasphemy.
A glass factory in the area told me that for industrial glass up to 19 mm has no problem providing it to me, already cut to size. Tomorrow morning if I can take a step to get me a price of two discs. If we are more or less around the figure you suggested, I take out my wallet and greetings.Hi Massimo, thank you, I'll start to qualify then! Seriously, not finding information about the Suprax on the schott website, I also thought it was no longer produced, so a friend called Schott directly to ask how to find Supramax with relative prices. He was told that Schott only sells to companies in the industry and that he could still have saved money by using Suprax only supplied in discs from 600 mm… But if you tell me that, you strengthen my suspicions…
I have toured a lot of glass factories in my area but everyone talks about thicknesses that do not exceed 19 mm and above all nobody deals with anything other than normal industrial glass. I would like to be able to choose diameter, thickness and quality of the glass but the Supramax and the Zerodur have really high prices. I have seen Supramax blanks since 300 mm thickness below 40mm to more than 400 euro… Without considering that at that point as a tool it would be crazy to use a twin disc
You who use?hello Giulio, thanks for the welcome! I have read practically all the articles here on grattavetro and I agree with you that, for us, the pursuit of perfection is almost a duty since we don't cost anything
The glasses they should get me are the records from 600 mm of Suprax which I will then have to cut to size. It won't be as good as Supramax or Duran but I think you can still make some respectable mirrors without fainting… especially at the beginning of my adventure.
I'll have to start from the initial rough, therefore the commitment will be greater, but it is not an open heart surgery… nothing serious can go wrong, badly it goes away! However, I didn't think it was that complicated to find glass!!!I live inland a 5 or 6 km from the sea… it is not really isolated countryside but not even a city and not having much experience I would not know how to assess the level of light pollution. The luck of Liguria is that in less than half an hour by car you can go from the beach to the mountains above 1000 meters with a pretty good sky. My ultimate goal would be to have something usable at home and something large in diameter to use for targeted outings. The planetarium interests me but in order of priority I definitely put in front of the objects of the deep.
Once I have clear which measures to choose I will start with a PC design of the instrument as a whole. As soon as I manage to get the glass, I will put the PC aside and start with the actual project
