You know you are close to the mark on that one.
What I could do to make my own mirror easily, is to make a mould out of cardboard which follows the elipse for a 12inch reflector for example. On top of the cardboard mould I place a layer of fibreglass resin and fibreglass to strengthen the mould. Then I progressively add layer on layer of beach sand.
I add an attachment to the mould which enables me to connect the mould to a rigidly mounted variable drill.
The drill is switched on with the mould attached, and the mould circulates round and round on a a bed of glass. Water is periodically added to keep the mould from wearing down too much.
Toward the end of the process finer and finer grades of emery paper are used until the eliptical surface is perfectly smoothe.
Voila! A 12 inch mirror for less than $50 plus a little money for coating.
Using the same principle it is possible to construct a larger reflector and use ones own house as the frame, a little bit like a sky light.
This is not my idea. It is originally the idea of Professor Robert Hooke.
If only NASA had looked at the work of Professor Robert Hooke, they probably could have saved a lot of money. They probably would not have built the Hubble Telescope either.
You see it is the case that Hooke's methodology allows for the construction of hugely immense telescope.
Imagine a tower telescope using the television towers in Brisbane as the frame for example.