can we use an ordinary mirror in a dobsonian telescope?

[yanesh]

hello well i want to use an ordinary mirror for use in the making of my dobsonian telescope. will it work?

[al_moskowitz]

No... Dobsonian refers to the way the scope is mounted. Optically, most (if not all) Dobsonians are actually Newtonian reflectors... The main objective in a Newtonian reflector is a parabolic mirror (thicker on the edges than in the middle, or, otherwise stated, a piece of glass with a curve carved into it, coated with a reflective substance.

UPDATE: And injanier makes a good point - the tolerances are very tight... I made a 6 inch newtonian when I was in Jr. High and believe me, you'd better pack several lunches - it's not something you do in a weekend...

[injanier]

The primary mirror in a dobsonian is a concave paraboloid, and the secondary is a flat. Both need to be first surface mirrors with a surface a surface accuracy of 2.5 microinches or better, so no, you can't use an ordinary mirror.