making parabolic mirror with resin

Jonathan B-C wrote:
I was able to find other groups (not google) that had some posts on
resin or plastic mirrors (sometimes with spin casting as part of the
topic). But many of these date back to 1998 or earlier. Has there
been lost of interest because it's difficult/not cost effective? Of
course, the posts were related to telescope-quality mirrors (couldn't
find the topic anywhere else), but again, I'm wondering if such
quality is necessary for the illusion. I guess that would depend on
the quality/sharpness of the illusion...

Bye the way, thanks Brian for the suggestions...


http://scientificsonline.com/product.asp?pn=3072381

This is what you are looking for isn't it ?

This company makes the resin cast mirrors you seek:

www.opticastmirrors.com

There was quite a thread about these a few years ago, but I don't recall
anybody actually making a telescope and reporting back on SAA.

Steve Taylor wrote in message news:3f963790$0

http://scientificsonline.com/product.asp?pn=3072381

This is what you are looking for isn't it ?

Yep! But I still would like to know why resin mirror seem like a
passe subject, and if there are ways to make deep paraboloic mirror in
one's garage quickly and cheaply....

Thanks,

jbc

In message , Jonathan
B-C writes
Steve Taylor wrote in message news:3f963790$0

http://scientificsonline.com/product.asp?pn=3072381

This is what you are looking for isn't it ?

Yep! But I still would like to know why resin mirror seem like a
passe subject, and if there are ways to make deep paraboloic mirror in
one's garage quickly and cheaply....

Depends on what quality of mirror you want to make. A burning glass
mirror is pretty easy to spin cast. But the image quality is dire.

It also takes so much experimentation to get anything even half decent
that it isn't cheap unless you have a free supply of resin and catalyst.
The big problem is plastics expand a lot as they cure and most systems
get seriously hot when curing in bulk. ISTR the recommended way was to
precast a rough "mould" and then cast a much thinner skin on top.

SciAM did an article on Amateur DIY mirrors in the same edition as they
covered the Canadian rotating mercury mirror scope.

A better option for a cheap mirror would be to find some pressed
aluminium packaging used for chemical plant bursting disks in a
junkyard. They are about 20-40" roughly spherical pressed aluminium and
then polish them up. They make interesting focussed solar cookers.

Regards,
--
Martin Brown