Just for reference, what the astronomer meant by "optical glass" is glass that has a good planar surface (less than 1.4 wave typ.) and also should be nicely homonogous consistency. Glass from the glass shop has been used as correctors by Celestron in thier earlier scopes but they are now using better quality glass. Probably the best way (if you are making an observtory is to put the scope outside and you inside of a building. See the Porter design which is basically a Newt. in design. The alternative which I use for Sou. Ca. (yes, we get quite cold down here, below 0f!) is a portable observatory.