Price of mirror blank

[dark star]

I finally got a reply from Spectraglass to my enquiry about the price of a 20 inch (508mm), 40mm thick glass blank for making a telesope mirror. The price is £381 plus £25 for delivery. Is this an OK price? In any case they are the only supplier of large blanks I know of in the UK! The glass is 43 Suprax 8488, which seems to be low expansion like Pyrex.

I am going to send an e-mail to someone in Germany who sells blanks asking the price. His website is called Stathis First Light and I have read a couple of reports on the internet saying the blanks are good. As I am planning on buying the pitch and grinding powders from him.

I previously got pitch from Galvoptics, but they seemed rather expensive, although perhaps pitch just is expensive? i would like to try some different pitch in any case ands see how it compares. There certainly seems to be a shortage of places to buy mirror blanks and pitch!

David

[mister_wavey]

Do please share the price you get from the Germans (or anywhere else). I have a half finished 6" I really should complete. A 20" would be something!

[ronin]

As you have a location of London have you enquired at this lot:

http://www.scientificmirrors.co.uk/Telescope%20Making%20Supplies.html

The blanks they list go to 250mm but may be worth asking if they have or can get larger.

They also list an assortment of powders.

They have an address of:

Vacuum Coatings Ltd (Scientific Mirrors)
66 Barrett Road
Walthamstow
London E17 9ET
Tel/Fax 0208 520 5353

Have a read, may be an option.

[dark star]

I got a quick reply from Stathis First Light. However the price of the 508mm blank is 885 Euro plus 88 Euro for 'fine cooling' to avoid stress in the mirror = 973 Euros which is around £765!

Making a 20 inch mirror at that price for the blank does not make any sense to me, so I will go with Spectraglass. The price of pitch and grinding powders from Stathis First Light may be fine, I just need to get some more details.

David

[dark star]

I go to the Camden Telescope Making Society in London and Terry of Vaccuum Coatings is their resident expert, his advice has been invaluable so far. He would have told me if they have any 20 inch glass blanks as he knows this is my next project. Spectraglass is the only source I know of for really large glass blanks in the UK. Especially as I want one 40mm thick and not 25mm. I am just grateful that there is one place in the country!

If I had a flat that was extremely large rather than small and a lot more money (and I mean really a lot more!) I would start fantasising about buying a kiln and making my own glass blanks!

David

[NickK]

I go to the Camden Telescope Making Society in London and Terry of Vaccuum Coatings is their resident expert, his advice has been invaluable so far. He would have told me if they have any 20 inch glass blanks as he knows this is my next project. Spectraglass is the only source I know of for really large glass blanks in the UK. Especially as I want one 40mm thick and not 25mm. I am just grateful that there is one place in the country!

If I had a flat that was extremely large rather than small and a lot more money (and I mean really a lot more!) I would start fantasising about buying a kiln and making my own glass blanks!

David

Especially as you could use the kiln to create lightweight mirrors, anneal, slump glass, heat the pitch, smaller cure carbon fiber composite components including mirror components.. although you'd not be able to use Pyrex in it..

[Peter Drew]

I think that by the time you've bought the kiln, learned the tricky art of annealing and paid the electricity bill, an off the shelf blank would start to look quite cheap.    

[Glasspusher]

As somebody that owns a kiln I have to say Peter has it spot on.

John

[dark star]

I received a Paypal invoice from Spectraglass for the blank. It turns out the price quoted did not include V.A.T. and the actual price is £487.20 including £25 for delivery! This is a lot more than I expected. I have sent an e-mail querying the price, as no mention was made of V.A.T. not being included in the price in the original e-mail. I am hoping it is a mistake!

However, if not, given that I do not know of another cheaper source I will have to pay it if I want a 20 inch blank.

David 

[mapstar]

I received a Paypal invoice from Spectraglass for the blank. It turns out the price quoted did not include V.A.T. and the actual price is £487.20 including £25 for delivery! This is a lot more than I expected. I have sent an e-mail querying the price, as no mention was made of V.A.T. not being included in the price in the original e-mail. I am hoping it is a mistake!

However, if not, given that I do not know of another cheaper source I will have to pay it if I want a 20 inch blank.

David 

Sounds about right to me as I paid about £470 for a 22" blank more than a year ago and think that is up to about £550 now?

There is a lot of work in one of those I'm over 100 hours into mine

Damian