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(2) Set a magnification at least 3 or 4 times higher than that will used for photographing.
(3) Obtain the thinnest over-focus (Fresnel) fringe that can be clearly seen in the binocular,
with beam spread. Caution: make sure you focus the binocular on the viewing screen.
(4) Adjust the OJB STIG X and Y (MULTIFUNCTION keys) until the fringe follows the
outline of the hole uniformly and symmetrically.
(5) Use finest focus step, go through focus series to check astigmatism correction.
Second Method (for specimens with few small holes or any specimen)
(1) Using any specimen, adjust (at the best focus) objective stigmators until image is as crisp
(sharp) as possible.
(2) Go through focus series to check astigmatism correction.
Third Method (for ultra-high resolution images, >150kx )
(1) Find the amorphous area such as amorphous carbon film or any amorphous contaminants
around the specimen or any amorphous material.
(2) If there is an appearance of smearing or some thing that looks like periodic structure
exists in the amorphous film, this is an indication of an astigmated objective lens. Correct
this by observing the amorphous image as the objective lens focus is changed.
(3) Correct astigmatism with the OBJ STIG X and Y (MULTIFUNCTION) controls. There
should be random grains in the structure/image of the carbon or amorphous film.
(4) Go through finest focus series to check astigmatism correction. It should have no more
“directional” on the image when changing focus.
Note: Be very careful about correcting the objective astigmatism. If it looks pretty good, you
may want to leave it rather than risk making it worse if you were not sure to make a better
correction. The objective astigmatism is most critical at high magnification imaging.
Final Comments
You are now ready to examine your specimen. During the examination/observation,
minor features of alignment such as eucentricity and astigmatism should be checked and
corrected from time to time. Take notes as detail and as much as possible while examining
specimen and taking photographs.
Happy Hunting and Enjoying the Small World!
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