Re: ATM "Buena Vista" home-made Plossls

["Chuck Hards" <chuckh@companionsystems.com>]

More news from American Science and Surplus:  The 28 x 57 achro, stock
#65171, has been discontinued.  They have nothing else even close.  This is
the lens I used for the 28mm eyepiece.  Too bad; this one is sweet.

I also obtained (2) #66266.  These are listed as 11 x 22 acros, but they are
actually an uncemeted, "contact" doublet.  When mounted, they produced a
badly distorted field.  Only a small central area was in-focus.  I tried
varying the spacing, and as the spacing opened up, the wicked field
curvature lessened slightly, but stilll nowhere enough to make it a usable
eyepiece.  I then tried combining the negative element of one set with both
elements of the other, in a "triplet" configuration.  This produced a lens
with essentially no power at all, and it was not usable, either.  One set of
elements alone produced a reasonable image, but the apparent field was only
about 15-20 degrees.  I pronounce this lens unusable.

I have noticed that Edmund has a good selection of achros in their "Surplus
Optics" section.  I plan on trying out a few of those, but they are
generally twice the price of AmSci & Surp., which effectively throws the
ecconomizing rationale out the window.

Chuck Hards