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First (& 2nd) Mirror Grind. Advice appreciated.


long_arms

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Hello :smiley: , 

My  200p has served me extremely well. But It's time for an upgrade and I don't want to buy another ready made telescope.

So... It's going to be a 12" F/5 (ish) newt. This isn't up for discussion. I know its big haha :p . 

Anyway, I've read my Texereau a few times and I'm ready to go. 

I'm going to start off with a 200mm (8inch) f/5 mirror. Not gonna jump straight to 12", plus the plan is it'll replace the one in my 200p once finished. 

I'm after some suggestions for the correct amount of grinding/polishing powders I should realistically buy? Just for the 8inch. I'm going to put time into it, aim for a great polish and figure. 

Also recommendations for suppliers of the blank/powders/pitch/tiles etc? I'll be ordering everything this week. Think I'll go for pyrex (or similar low expansion glass). 

Not sure what I'm going to grind them on. But I'm quite tempted to buy an old Oak Barrel. If anyone has good suggestions for a cheap but sturdy table thats up to it let me know. 

Thanks, 

Dan  :smiley:

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  • 2 weeks later...

good luck dan and welcome to the world of mirror making.

as an amateur myself, grinding my first mirror(check out my blog for my grind diary) I cant offer definitive advice but here's my 2p anyway.

firstly I would just start with the 12" rather than the 8"

blank-I would get a 12"x25mm thick Pilkington glass blank from somewhere like galvoptics.these can be had for £50 and are thick enough for your F5 build.you could go for a thicker low expansion one but this would up the price to £268 for a 40mm one,quite a big jump you would agree.heres a link http://www.galvoptics.fsnet.co.uk/telescope3.htm

for grits have a look at UKGE http://www.ukge.com/en-gb/Lapidary/Grits,-Media,-and-Polish__c-p-0-0-14-243.aspx and I would get 3.5kg of 80 grit and then small amounts of 220 and 400.you then need some 600 aluminium oxide and then some cerium oxide.probably only a couple 100 grams of each.some cement for a tile tool.a kg of pitch will be plenty enough for a 12" tool.

for a 12" you could grind it on a black and decker workmate with the supplied clamps or with a piece of work top clamped onto it.

buy a few sharpening stones like this http://www.ebay.co.uk/itm/8-COMBINATION-SHARPENING-STONE-FOR-COARSE-GRITS-CHISEL-BLADES-KNIFE-SCISSOR-/181335927954?pt=UK_Collectable_ToolsHasdware_RL&hash=item2a3876ac92  for bevelling.

read and ask as much questions as you can

hope this helps get you started

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Hi Dan

Agreed with Rich above and welcome to the world of the grind.

Plenty on here will offer help and advice when you need it. Texereau is a little on the dated side now. I read a few bits from it and there is still some useful info in there but there are other ways to create a mirror rather than just what the book says.

Stellafane and new port glass have some good reading on there too

Damian

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