Re: [ATM] Conical mirror question

["Thomas Janstrom" <thomas@moiler.com>]

For one I would question the thermal properties, even with the conical
cross section, the surface area to volume distribution isn't even, the
centre section will take longer than the outer zones to reach
equilibrium. 

The conical mirror blank is best suited for Cass type systems (in my
opinion anyway) where the central baffle tube is also the mirror
retainer, you still need a cell to allow you to collimate the system, so
your not gaining all that much by going this route. The only real gain
is no mirror clips to warp the mirror, but that bolt he show on his site
will do that too if your not careful, or worse break the whole thing, I
didn't see any cushioning between it and the mirror, just a couple of
steel washers.

Any way that my $0.02 worth, they are a good idea in the right
application...

Cheers, Thomas.

-----Original Message-----
From: atm-bounces@atmlist.net [mailto:atm-bounces@atmlist.net] On Behalf
Of Mike Shuken
Sent: Saturday, 22 April 2006 5:49 PM
To: atm@atmlist.net
Subject: [ATM] Conical mirror question

Hello,

Has anyone purchased a conical mirror?

I was looking at this website - seems to be some very well made 
mirrors for Dob building, they charge about $50 more for a conical
mirror.

http://www.rfroyce.com/conical/

Any reason why it would not be better to go with a conical?  The 
*single bolt* mount to the cell seems pretty nice for amateur 
builders, makes the cell construction easier - and the "info" page on 
the website says that it is much sturdier and needs less collimating 
than standard thickness mirrors.

Less weight also, that's kind of nice.

What downsides am I missing here?

Thanks,

Mike
California


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