Re: [ATM] lurie-houghton progress

[Guy Brandenburg <gfbrandenburg@yahoo.com>]

I know about the spheres being the same radius. The
concave curve was all weird in the Ronchi test,
looking something like a 'zulu shield' to borrow a
phrase from Dave Harbour. Given that the concave one
was all weird, it was doubtful that the convex one
would mysteriously match it!

Once the long-FL concave surface is decent, we'll have
to do some trial and error to figure out what to do
with the convex surface to get it to match the concave
surface, as shown by straight interference fringes
under the monochromatic light source. Anybody have
practical experience with that?

>From my experience, it almost does seems that the
shorter the f/ ratio, the easier it is to make a
sphere. Many of the scopes that have had the worst
problems arriving at a sphere have been the f/10s and
f/9s. This f/4 or thereabouts sphere has been the
easiest sphere I've seen so far. We'll see what
happens in the future.

The glass for a LH doesn't have to be expensive at
all. Plate glass would work fine, as long as it
doesn't have strain. The only thing is that it's not
terribly transparent.

Guy

--- Bob May <bobmay@nethere.com> wrote:

> Guy, not only do the two spheres need ot be
> spherical but thay also need to
> be the same radius.  I suspect that your 20' ROC
> curves dont' match each
> other os you're getting the rings.  The solution
> there, of courese, is
> obvious and not difficult to do.
> The very small ROCs, are easier to polsih spherical
> more because the forces
> keep the lap spherical which reproduces itself on
> the glass.  That sort of
> effect tho doesn't start to really work until you
> get to really short ROC
> curves and 5' isn't naywhere near ther.
> I had a guy appear at my class a few times that was
> considering doing a
> Houghton but he was more of a dilentante to the
> whole thing and nothing ever
> went anywhere.  I think that he got scared off by
> the price of the glass and
> the fact that he'd have to actually push glass.
> Bob May


Guy  Brandenburg
Washington, DC
My home page:
http://home.earthlink.net/~gfbranden/GFB_Home_Page.html
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