Hi from the UK . The mirror making machine related posting pointed me back a few years . A couple of Liverpool lads had (if memory served me right) used an angle grinder on an arm to hog out a BIG mirror . It was usable (but astigmatic) and their old TROK website had gone. They have moved on to newer BIG scopes , methods and a new website .
The bit reffering to the new grinding/polishing machines is here:-
http://datscope.wikispaces.com/New+grinding+machine
Plenty of interest to me on their website . You may find the same !
Best wishes ,
Len E