[3dem] astigmatism in low mag mode?

[Schwartz, Cindi (NIH/NIAID) [E]]

Hey David!

That happened to us. Put in a 200 mesh grid (either holey carbon or cross-grating), highest LM mode, then make it eucentric and in focus. Use a continuous imaging mode and live FFT (in SerialEM) and turn on diffraction stigmators. Then stigmate away. I don't know how we lost our either. But it's relatively easy to get it back once you know how.

Cheers,

Cindi L. Schwartz
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From: 3dem <3dem-bounces at ncmir.ucsd.edu> On Behalf Of Morgan, David Gene
Sent: Thursday, April 18, 2024 5:30 PM
To: 3dem at ncmir.ucsd.edu
Subject: [EXTERNAL] [3dem] astigmatism in low mag mode?

Hi,

Has anyone else encountered terrible astigmatism in low mag mode on a TFS microscope?  We have run into this multiple times in the last several months on our Talos Arctica, and I am trying to understand what is causing it and how we can prevent it.

While looking at this problem, I also realized that I have no idea what lenses are changed when the focus in low mag mode is changed.  I grabbed several screen shots of the "system tab" in the TFS UI, looking for changes in the lenses and deflectors reported there.  Nothing seems to change, even though the images clearly change and the microscope reports defocus changes that seem to make sense...

Any thoughts would be appreciated.  Thanks in advance.
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            David Gene Morgan
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