Sniker, sniker! I wonder about your Telescope shop. As you knew there is a difference between spherical and concave. It is true that a mirror can be concave or convex, and spherical _at_ the same time or some other figure -parabolized, hyperolized, elipsoid and what ever the the maker left it in. Spherical may be ok if the focal length is long enough. Try to find out what FL your mirror is and then ask if it is good enough.
BTW, did your Telescope Shop test the mirror to tell if it a sphere? They have pretty good eyes if the didn't test it. I'd suggest a Ronchi test to see if the dark lines a straight in the side or if they are slightly curved. don't give up as you may have a useable mirror after all.
Bob
):-{])) <---- madden@netcom.com madden@svpal.org Remember amateur astronomers: "keep looking for the next Universe"
On Sun, 23 Jul 1995, Alan D. Cline wrote:
> I would like to make a telescope and I found a mirror about 7" from an old
> piece of medical equipment. I brought it to an astronomy shop and they told
> me that they had both good and bad news. They said that it it a good
> mirror, of good optical quality, however they said that it was spherical and
> not concave. It sure looked concave to me, so I am not sure what they were
> talking about. They told me that I could build a telescope with this
> mirror, but I would have to drill a hole in the middle. I would like some
> advice and enlightenment into what would be the best route to go with this
> mirror.
>
>
> Please reply if you have any information.
>
> Thanks in advance.
>
> I just wanted to note that it is unfortunate that people have to post
> garbage mail (OLGA CRAP). I guess some never grow up and/or learn what is
> and is not appropriate!
>
>
>
> Alan Cline
>
>