[3dem] Dose-symmetric tilt scheme for electron cryo tomography

[Davide Floris]

Dear Ben
after reading with a colleague the description (see forwarded message) you sent me, we noticed that the point 2) mentions as “CountTarget” the number of counts per image, while in the script it says #set target counts for tomogram, and the default value is set to 100.
We are wondering:
- is the value referred to the single image or to the whole tomogram?
- is “counts” to be intended as “electrons” or it must be converted into electrons?

We use a K2 summit in super resolution mode, but don’t know which camera was used to test the script (Falcon, CCD, K2 in linear mode?).
Could you give us any clarification?
Best,

Davide
_________________________________________________

Davide Floris
PhD student
Max Planck Institute of Biophysics
Structural Biology Department
Max-von-Laue Straße 3
60438 Frankfurt am Main
Germany

(L2.090): +49-69-6303-3037
(B2.205): +49-69-6303-3049

> On 22 May 2017, at 11:27, Ben Engel <bdengel at gmail.com> wrote:
> 
> Hi Everyone, 
> 
> as promised here is a version of the Hagen tilt scheme that I modified so that it can be started at any starting angle.
> 
> For lamellae, the pre tilt is 7 º, i.e. if you’re milling at 18º, 11º stage tilt should be your actual ‘0º’. I routinely use a starting angle of 10º,
> 
> and this results in virtually the same number of counts when tilting +xº and -xº from your actual zero.
> 
> 
> The procedure to use the script is as follows:
> 
> 0) Set up your SerialEM session as usual.
> 
> 1) Copy the contents of the file to an empty macro slot and change parameters as needed. (Once you save your settings the script will be there permanently)
> 
> 2) Check and adjust AngleOffset (your starting angle), CountTarget (the number of counts you’re asking for each image), step (the angle increment) 
> 
>     and tilttimes (how many times the script will do +step -> -step -> -2*step -> +2*step, e.g. for step = 2, tilt times = 15 you will get ±60º around your actual ‘zero’)
> 
>     Make sure you’re not exceeding the stage limits!!!
> 

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