To: rhill{at}lpl.arizona.edu, atm{at}shore.net
From: mdholm{at}telerama.com
Reply-To: mdholm{at}telerama.com


Richard Hill wrote:

>I first knew Art back in the 1960s but lost touch in the 1980s. Is he still
>around? It would be great to send him a letter telling how we used his design.

My information is that Art Leonard died in October 2001.  He had been
living in Washington state.  I got this info from someone at the Sacramento
Valley Astronomical Society, of which Art was a member for many years.

Art's Yolo Booklet http://www.atmsite.org/contrib/Holm/yolo/index.html
shows two styles of warping harness.  The more complex style is designed to
keep the weight of the harness from affecting the result.  Art wrote that
aluminum might have allowed the simpler harness to work in larger sizes,
but the coefficient of expansion of aluminum is too high.  He used steel
despite it's higher weight because it has lower expansion.  With carbon
fiber composites, one might be able to get low weight and low expansion in
one package!  Thus, one could use the simple design, perhaps even on larger
Yolos.

A couple of ATM's have used materials glued to the edge of a mirror to warp
it, either during figuring, or during use.  (I'll try to remember to post
references in another message.  I am away from the info right now.)  This
approach would minimize extra bulk of the harness.  One could even use this
approach to correct astigmatism in a Schiefspiegler instead of using a
tilted lens.  Anton Kutter tried this approach in the 50's, but found the
warping harness to uncontrollable.  Leonard's experience with the Yolo
indicates that a warping harness can be produced with acceptable stability.
 Some of Art Leonard's ideas for the details of the harness might overcome
the problems Kutter encountered.

Mark Holm
mdholm{at}telerama.com

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