Need help in making my 1st telescope

[Rock™]

Hello everyone, i am new to the astronomy so i would like to ask 2 silly question and i hope you all will not mind.

1. Glass that we use to make telescope mirror, can it be of any kind or there are different kind of glass?

2. I have 1 sqare feet and 12mm thick glass,can it be used to make mirror? if yes, then which diameter should i cut it?

thanks in advance.

[Daniel-K]

The ATM Site: Resources and Techniques for Amateur Telescope Makers

lots of info here im using 1.25 inch plate glass to make a 16inch mirror. you will need to do some research about focal length and f numbers to decide what size of telescope you want to make. you will NEED some sort of plan to get started

[NGC 1502]

In the early days of telescope making, almost any glass was used, "porthole" glass from ships was one source.

These days, two types of glass are used by amateur telescope makers, plate glass and low expansion glass. Low expansion glass is probably best, but many fine mirrors have been crafted using plate glass.

From the glass you have, I would cut the largest diameter you can. Don't forget you will need another disc to use as the tool.

I've no idea how to cut it however.

All the best with the project, Ed.

[Rock™]

@ NGC 1502 @ i was asking that what should be the diameter of glass? for example 4" or 6" or 8".

[daz]

Well, do you have another sheet from which you can cut the tool?

If not, then you'll need to cut both from the same sheet, so 4" is probably the limit...

What type of glass is it?

What focal length are you making?

[weareborg]

Cut the largest size you can from the sheet. You can always make your tool using something else. A tile tool works well

Andy

[michael.h.f.wilkinson]

I seem to remember that the thickness of a mirror should be in the order of 1/6th to 1/8th of the diameter, in order for it to be stiff enough. Better mirror cells may have reduced the need for that type of thickness. That would yield no more than 4" for 12mm of glass. Low expansion materials like Pyrex (used in the Hale if I am not mistaken) and nowadays Zerodur and fused silica are used in professional scopes.

[Rock™]

I seem to remember that the thickness of a mirror should be in the order of 1/6th to 1/8th of the diameter, in order for it to be stiff enough. Better mirror cells may have reduced the need for that type of thickness. That would yield no more than 4" for 12mm of glass. Low expansion materials like Pyrex (used in the Hale if I am not mistaken) and nowadays Zerodur and fused silica are used in professional scopes.

Thats what i was asking my friend. ;)

It means that 12mm glass should be 4" diameter not more than that. thanks once again.