Tasco objective

So I've disassembled my Tasco's objective today. Turns out it doesn't
have a separator _between_ the two elements. It has two plastic
retainers above and below the two elements, so that the cell and screw
ring does not come in contact with the lens surfaces.

I can also see some Newton's rings between the two elements when in
contact, which change shape when one of the elements moves or slides
along the other.

It appears as through the elements are airspaced, but the contact is
pretty tight. The elements separate, but when placed together the
induced vacuum tends to keep them together.

I lifted the elements and placed some paper pieces at 120 degree angles
and did some viewing of some distant light sources. My impression was
that the paper spaced objective gave a slightly sharper definition
between closer points. That is, my impression was that the separation
limit increased somewhat.

Questions:
1) Is it right to lift and separate the two elements with paper, if the
objective is designed to be airspaced? Can performance improve that way?
Any test to objectively measure such a change?

2) Defocusing distant points' images, I get circles when the image is at
the center, but elipses when the image moves near the edge of the
Tasco's field, when I move the scope. Two months ago I sawed the tube in
order to shorten it and I might have placed its focuser slightly
non-perpendicular to its optical axis. Does this have to do anything
with the distortion?

Thanks in advance,
--
I. N. Galidakis
http://users.forthnet.gr/ath/jgal/
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Eventually, _everything_ is understandable