Can a magnifying mirror be practical as a reflecting telescope's primary mirror?

[Vincent L]

I can't find any good scope seller or an optical shop in our place that sells customizable mirror. I'm planning to buy a magnifying mirror and use it as a reflecting scope's primary mirror. I've heard that the focal length might be short. How short is an average focal length of a magnifying mirror? Is it too short to be used in a telescope or passable as an average quality scope mirror? I haven't bought one and measured it.

[Nick F]

No it is totally unsuitable. Its refelctive surface is behind the glass for one thing, its shape is far to crude for a telescope it will never focus reasonably if at all

[Philip J]

When you say "magnifying mirror", what comes to mind is a shaving mirror or perhaps the mirror used in an overhead-projector. These mirrors are extremely poor optical quality. For astronomy, you must have a precision ground mirror. If you can't find a used one cheap, then your best bet is to grind it yourself. Here are some links to do-it-yourself telescope building and mirror grinding.