Hi everyone

[Carlo A]

Hi everyone, my name is Carlo, I'm from Cursi in the province of Lecce, I'm new to astronomy and have never owned a telescope, although I have always had the idea of ​​buying one but never did . But for some time (I came across this site by chance) I follow this forum and I said to myself “why not!”, since I like building things (failures and successes) making a telescope would be a great undertaking.
So here I am.

[Giulio TiberinI]

Welcome Carlo!
IF you already have some ideas, expressive, so it helps us help you.

In fact, building a Dobsonian Newtonian telescope is the simplest way. What is much more challenging is also building the primary mirror, which can also be conveniently purchased second-hand, and inserted into the structure “do-it-yourself”.

[Carlo A]

I also intend to scratch the primary mirror, I was thinking of a compromise between construction difficulty and performance at a 250mm with normal 20mm glass.

[Giulio TiberinI]

I'd say the right choice. A 250 Lightened F5 is a good start, o f6 o 6,5 not lightened, it is not only a good start but also an easy and safe quality result.

[Carlo A]

Grit silicon carbide arrived today 60 1kg and money 80 1kg.

[Giulio TiberinI]

You already have the disc (or the two discs) glass diameter 250x20mm?

[Carlo A]

I hadn't yet waited for a communication from a glass factory, still nothing

[Bartolomei Mirco]

Hello Carlo,
Welcome to the forum from me too!
Excellent choice to start with a 250 f5
Excellent relationship between probability of success and observational satisfaction given by the chosen diameter.
We hope the glasses arrive quickly, this is how it begins
Hello and see you soon
Mirco

[Carlo A]

This week they deliver the two glass discs 255*20mm with 3mm bevel

[Giulio TiberinI]

Very good Carlo.
At this point, all you need is the workbench to get started “round dance” around.

There, too, there is a possibility of choice, whether to use the former mineral oil keg with multilayer lid to work standing up, or the bench like John Dobson to work seated.

Everyone has their preferences. I have always used the barrel because it allows you not to dirty the environment beyond the table itself, always easy to clean. And I was even better walking around it. While the bench is apparently more comfortable, but it is easy to dirty the floor .. What I would have found the veto on “landlady”( ), even though I've always done the work in the boiler-washer-ironing room.

[Carlo A]

Retired glasses, workstation under construction

[Giulio TiberinI]

Well well Carlo!!

Since you already have the abrasives 60 e 80 for roughing with the “cord races”, I can advise you (if you have not already done) to read this article to you:

How to build focal lenght and mirror's depth.

which will help you avoid the common mistake of struggling to reach the spherical cap with the desired depth of arrow in the center of the mirror (which is 3.12mm for a 250F5 mirror):

During the reading, you will also find the link to the article on chordal passages that are used to efficiently excavate the spherical cap.
You will see that you will get there soon.

[Author]

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