Nope, will not be lubricating the process with sweat of brow, first thing is to make a lens grinding machine.
Starkler's comment is interesting, I read about coma in the context of someone saying it was a sign that the light wasn't hitting the mirror square. Which would be fixable. But then it was suggested it was native to all parabaloid mirrors.
Light from a star at the edge of the field of view isn't striking the mirror squarely, I suppose.
Funny that I've never heard of it before.