[3dem] Objective Astigmatism Stability

Tue Aug 20 15:00:41 PDT 2019

Dear Farzad,

Our "full-dataset CTF" determination/correction does an automatic
determination of all images (or all movies) of a full cryo-EM data set all
at once (Afanasyev et al. 2017
http://journals.iucr.org/m/issues/2017/05/00/kf5002/index.html). You can
thus quasi automatically obtain CTF/astigmatism assessments over all large
cryo-EM data sets you ever collected.  Since each data set may have been
collected over days you could thus effectively measure how much the
astigmatim typically changes over time. Moreover, the approach integrates
all spectral information in the data over the full data set and is
therefore "infinitely" more precise than any CTF assessment of an
individual image or movie.
Cheers,
Marin

On Tue, Aug 20, 2019 at 6:43 AM Farzad <farzaad at gmail.com> wrote:

> Dear All,
>
> Anybody has any experience in measuring the stability of objective
> astigmatism in FEI F20 FEG columns (Tecnai, Talos or Glacios)? How much let
> say "astigmatism drift" is normal if we do not change anything and come
> back to the instrument after 15 minutes. I mean just imagin after
> correcting it on a carbon film area and check it on a same region and same
> optical set-up after a certain time?
>
> the sample is normal carbon grid, no magnetic or loos particles there, and
> also there is no major sample drift.
>
> Regards
>
> Farzad
>
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