Re: [ATM] first light on a Lurie-Houghton

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

The two concave surfaces can be chcked on the Foucault tester for
accuracy.  The two convex surfaces do need to be placed against
these concave surfaces and the accuracy of the rings checked.
Please note that if you just grabbed some plate glass, you won't
be able to do a good corrector unless you happen to fine some
that has excellent homogenity in the glass.  The refractive
indexxes and dispersion need to be the same for both pieces of
glas so you really need to have the papers on both pieces.
Differing glasses, i.e. not from the same melt, will cause
problems with the color correection.
Seeing a steady distortion in the image will be a function of the
corrector or the primary just as you would see such a distortion
in a regular newtonian mirror.  If you're seeing moving
distortion of the image, you've got tube currents and those need
to be addressed with fans or something else like that.
And yes, the R5/4 curvbes mostly change the FL as they differ
from each other.
Bob May
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