Re: [ATM] Patterns of Testing: how we are messing up the hobby

["Bob May" <bobmay@nethere.com>]

Wood not rigid enough???
The only tester that I've seen that was decently sturdy was the one that
Gene Larr brought in once (claimed that it was the tester used on the 200"
Palomar telescope mirror).  That thing was probably 20 lb. of brass!
All of my testers are made of wood, many of them are the cheap pine and all
can hold a nice well shaded image for as long as I want them to.  I have
more trouble with concrete floors moving than the wood of the tester
changing things!
BTW, I've also seen a lot of metal testers that were so flexible that you
touch them and they move the shadow image.
As to pitch laps, thin and soft works about as well as very thick and hard.
The ultimate flow is probably going to be about the same between the two and
that is what is needed to do the polishing and figuring.
Bob May
bobmay@nethere.com
http://nav.to/bobmay
http://bobmay.astronomy.net

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