objective aperture position

[Philip Koeck]

Hi,

I'm wondering whether our objective aperture is correctly positioned (or the
column
correctly aligned).
If I focus a diffusely scattering specimen at the eucentric height and then
switch to diffraction
mode with a relatively parallel beam (the beam covers the entire screen at a
magnification of
about 30K) I can't get a sharp (minimal) central spot and a sharp image of
the aperture
at the same time.
Is there something wrong with our microscope or with my idea of electron
optics?

sincerely,


Philip Koeck
Svdertvrns Hvgskola and
Karolinska Institutet
Dept. of Bioscience at Novum
S-14157 Huddinge
Sweden
phone: +46-8-6089186
fax: +46-8-6089290
http://www.biosci.ki.se/em

The phrase 'We have always done things this way.'
is as much a reason to change as a reason not to.
- Dartwill Aquila
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