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f. UNDERFOCUS the image with the Focus knob (turn counter clockwise from the
crossover) to obtain a few Thon
rings.
g. PRESS the Stg button to OPEN
the Stigmator Control page. If it
is not already highlighted, PRESS
the Obj key on this page.
h. With a live image on the CCD
camera, adjust the shape of the
Thon rings until round using the
objective stigmator with the
Multifunction X and Y knobs.
B. Using the Image on the Fluorescent Screen
a. SELECT an area that may be imaged at high magnification without damaging any
desirable portions of the specimen. Increase the magnification to 175,000x or higher
and adjust the illumination so the substructure or background grain i.e carbon support
film may be observed easily. The Intensity will have to be modified and the electron
beam recentered using the Shift X/Y knobs (Deflectors) as the magnification is
increased. This latter function may alternatively be controlled using the RST button,
on the panel to the left of the column.
b. SET the Focus Step size to 2 and OBTAIN a slightly underfocused image for maximum
contrast.
c. PRESS the Stig button to
open the STIGMATOR
CONTROL page. If it is
not already highlighted,
press the OBJ key on
this page.
d. USE the Multifunction
X/Y knobs, one at a
time, to obtain the
sharpest possible image
of
the
substructure.
e. VERIFY any astigmatism
has been corrected by
varying the focus (back
grain
2017.07.07
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