Making your own mirror blanks

[weareborg]

I always wondered if this was possible for an amateur to do at home but I had never been able to find much info on the topic over the past years. Then just the other day I came across this new site

How I make Telescope Mirror Blanks

It now seems that it is in fact possible for ATMer's to make ther own mirror blanks. Ok, so it may not be very cost effective if your just going to make 1 or 2 mirrors but I would of thought that if a club got together and did this, then surely the initial outlay would surely be well worth it. Just think of how many homebuild scopes you could build!!!!!

[Demonperformer]

Very interesting link ... thanks for posting it

[Merlin66]

back in the 70's we couldn't import astronomical equipment into South Africa so we started to cut our own blanks from porthole glass (1" thick) we made up a trepanning head and cut almost 100 blanks over the years. Didn't think of fusing them...good idea!!

A few years ago I did try to make an 18" slumped blank from a piece of 6mm glass...that would be extra lightweight!!!

After investing a few $$$$ it became obvious that there was no way it was going to work without machining a proper support plate; that was going to cost a few hundred dollars!! So that was the end of that.

[FraserClarke]

Nice Always interesting how far people will go in telescope making -- not seen anyone gathering up sand on the beach to melt down yet (though there are some videos on youtube of people casting their own blanks from broken glass -- scary stuff when it runs all over the floor!!).

Interesting that he is aiming for 'full thickness' blanks (I assume he means the traditional 6:1 ratio) -- I think that's a bit out-dated these days, now that we've worked out how to support mirrors properly. Still, will be very interesting to see what his result as like -- thanks for posting the link

I have a 9-inch fused blank sitting in my garage that I was very generously given by Richard Schwatrz about 15 years ago. It's made of 6mm plate glass, but with a complex ribbed structure designed to make it stiff enough. I don't know if he is still doing these? I never got round to working it , but it's high on my list now I'm getting back into telescope making. Think it will be 'interesting' to work to avoid getting print-through from the ribs....

Have you still got a kiln that could slump an 18-inch blank Ken?? 6mm maybe a bit thin, but something like 19-25mm plate would be very interesting as a menicus primary -- especially if you can work out how to polish it well at f/3 or faster...

[Ags]

back in the 70's we couldn't import astronomical equipment into South Africa so we started to cut our own blanks from porthole glass (1" thick) we made up a trepanning head and cut almost 100 blanks over the years. Didn't think of fusing them...good idea!!

I tried grinding one of those porthole blanks as a teenager - a 150mm blank. I kept getting scratches at the fine polishing stage. :-(

[Merlin66]

I was using the "services" of the local ceramic pottery factory ( just across the road from my son's factory in Melbourne) they could fit up to 24" diameter in their kiln. used it for pottery as well as slumped glass decorations - very nice stuff!

[Peter Drew]

I have a 42.5"diameter x 3" thick BVC (black vitrious ceramic) blank made in Canada which has been fused from several thinner discs. Prior to ordering it, I had a 18" test blank of the same material and produced by the same process made into a successfull F3.5 primary by Jon Owen of Halifax. In the 1970's when I shared a workshop with Jim Muirden, he made a 18" blank with two 1/2" thick discs bonded either side of radial strips of 1/2" x 2" deep plate glass as separaters. This was ground and polished to a recorded figure and checked again a year or so later. It appeared to retain the figure with no noticeable rib print through. Apart from the fun of trying to cast your own mirror blank, I suspect it would be cheaper, safer and quicker to purchase a ready made one in the "normal" sizes. .