I have taken it apart to clean it once and had no trouble getting everything lined up again. The mirror itself is rather easy to work on and the mounting assembly for it looks like it could easily hold a bigger one with minor dremel work.
I am just not sure who makes a fair mirror for this type of application..
Hold on thar bobalouie!
I was not playing grammar cop, I thought you meant that you would use a mill, I thought a lathe was easier. I also mentioned that I am not very good with milling, so I assumed you had milling methods that I have not yet learned. Actually all my metal work techniques are self taught so I am sure I do many things incorrectly.
I am by far a metal working expert and would not dare claim to be.
I could mill it out I guess. I was just having some fun.
There is nothing wrong with self taught. Some of the most interesting, informative, and capable people I know are self taught in there areas of expertise.
I have a rotory table for my mill so its not hard to do stepped circular shapes or compound angle cuts. Machine work is a low priority hobby of mine.
Most of what I do make is one off custom parts, replacement parts for obsolete items, or redesigns of poorly made factory parts using better materials. (I tend to do that a lot!)
I think with a mill and a lathe, one is empowered with a great tool, capable of a great many things. One being making car hardware when it is not easily on hand or at the local Autoquest, and really handy for projects. I love working metal... Great relaxer for me. It is just so messy though, I hate that part.
If you install a larger mirror the focal length will change unless it's concaved in such a way to be able to precisely focus on the diagonal mirror, thus allowing you to use the same tube.... but that's likely not possible. The extra space around the present main mirror is to allow for expansion and contraction of glass and body tube materials... and yes they do change dimensions slightly as humidity and temps affect them. Also use a microfiber cloth for cleaning optics and wipe lightly horizontally across the lens coatings, never in circles!
Dobsonian type scopes are easy and cheap to build and set up, and you get a lot of performance bang for your dollars spent. Drawback is their mounts are not capable of motor drives and their open design accumulates dust and moisture easily.
Reflector types gather tremendous light allowing you to see many faint objects. They are somewhat bulky but they are easy to view through and perform well.
Schmitt Cassegrain or Muskatov types are nice and compact but heavy for field transport. They are a sealed design and are costly due to the optics arrangement and internal necessities. They perform well also.
Refractor types provide very crisp images when image corrected via proper lensing. They are a pain in the neck literally when looking straight above unless the mounting system is high enough off the ground. They process the greatest amount of incoming light despite their smaller diamater lenses. The light doesn't scatter as much. Most refractors yield satisfactory images with color abberations. Apochromatic types with Ritchey Crucian optics solve that problem at the additional expense of your wallet. They excel at showing deep sky objects.