Jon Isaacs, I do not understand the logic of your comment.
It's obvious that the finish is corrupted hence it must be restored.
If in the process the mirror needs refiguring, then isn't that just what one does with any type of mirror?
And finally, is the intent of your comment to discourage me or other amateurs from trying, learning and doing? Should I just give up and go out and buy something new that someone else made?
A glass mirror does not corrode or lose it's figure. If the mirror needs refiguring, it is because it wasn't made properly in the first place. The surface of a poorly figured glass mirror will probably still be with 1/4 wave of light.
The surface precision needed is about 0.000025 inches. A hair is 0.004 inches.
My hope is that you understand the enormity of the task you are facing.
Very well put Joe, thanks.
In the end however, consider that
1. I have these two mirrors that are worth say, $X as scrap.
2. If one or both of the mirrors ends up a disaster and completely unusable in a telescope because I am "not a trained optician with years of experience" then
3. the mirrors are still worth $X as scrap and
4. I most likely have learned a lot.
As Joe said, I am trying to provide a dose of reality. What you have are two pieces of aluminum. they are not mirrors and it's most likely they never were, at least mirrors of sufficient quality for optical wave lengths.
Assuming the focal ratio is F/3, making a 24 inch F/3 mirror of sufficient optical quality for a telescope is a project for a very experienced optician, its far from a beginners project. There are many ATMs and commercial opticians in this forum. I think every last one would consider a F/3 24 inch mirror a very difficult challenge.
If you really want to make a serious attempt are turning one of these pieces of aluminum into a mirror, the first step would be to put them aside and learn to make a small, relatively slow mirror so you have some understanding of the techniques and skills required. You will learn how to test the mirror and to interpret the tests so you can figure the mirror to the extreme precision required.
Again, I'm not trying to be a Debbie Downer, I'm trying to add a dose of reality.