(c)
Rotation Center alignment:
Find an identifiable object in your specimen.
Click on
Rotation Center
and minimize its displacement using MF X and Y.
(d)
Comma free alignment:
Use the Orius CCD to go slightly underfocus (-500
nm). Using the live FFT correct
Direct Alignments
:
Comma free alignment X
and Y
. Make sure the alternating power spectra show the zeros at the same
frequencies.
Once you have performed the Direct Alignments click on
Done
to exit.
5. Centering the objective aperture.
At a magnification of 50000x press the diffraction button on the
right control panel. Insert the
objective aperture in (slide left) and using the aperture position knobs on the aperture
center it around the center of the un-diffracted beam.
6. Objective lens stigmation.
To stigmate the objective lens go to 50,000X, start the Orius CCD and set the focus to
slightly underfocus on the carbon support and bring up a live FFT so as you can see 2-3
Thon rings. If astigmatism is present these rings will be oval. To make the rings circular go
to the
Tune
tab in the
Stigmator
panel, click on
Objective
to activate the objective
stigmators. Use MF X and Y knobs, one at a time, to make the rings circular. If the rings
are not visible due to severe astigmatism either reduce the magnification or defocus further
and then stigmate as before. Once finished click on
None
