[Wavytone]

Hi Alex, The only reason to recoat a mirror IMHO is because the cost of a replacement would be prohibitive vs recoating, and I suspect the chaps at Bintel would know the answer to this.

Yes, as you correctly point out most epoxies will be a no-no when it comes to recoating, if the owner wanted to have this done. While there are vacuum epoxies there is no evidence these have been used. When I posed a question to Royce a couple of years ago they replied most mirrors are not recoated in their useful life, and they don't consider it warranted, particularly if they have had an SiO2 overcoat applied. Hence they glue the central stud in the back of some of their conical mirrors.

Secondly the cost of the chinese Newtonian scopes is so low that it raises a big question about the cost of replacement mirrors from the factory - if one was available. When you compare this vs the cost of freight, plus the cost or recoating (assuming it is done in Australia by a credible optical shop) it would be cheaper to toss the mirror and install a new one from the factory. In some cases its probably cheaper to replace the telescope than recoat the mirror.

It does make you wonder what the average life of a commercially-built dobsonian telescope is. My guess is the vast majority sold are used perhaps a dozen times, after which the owner loses interest and stashes them in a garage or storage until either it disintegrates and is trashed, the remaining bits & pieces flogged off or disposed of as junk.