You could with a dremel, a diamond cutoff wheel, and the Zinc Oxide bits for the fine trim but it would be far from perfect. One slip and the optic is ruined, Plus you would have all the fine glass powder to deal with which will cut into your skin and is very hazordous to resperation.
"[size=-1]Ordinarily, I could do it with a piece of Transparent Aluminum..."
But we're about 140 years too early for that, and you may get metal poisoning from the shavings as well.
The prefered method would be a high pressure water cutting system. I've seen these cut through 1" thick glass no problem
Next choice would be a laser, but it takes something in the megawatt range to cut through glass, if you can get the beam that narrow for the size of the optic.
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