[3dem] gain reference for new ultrascan 4x4

[Ruben Diaz]

Hi Alexandra,
Alexandra,

We also have a 4kx4k  Gatan ultrascan, although I would not say it is a new one anymore. There are two things that one has to do for the proper operation of the camera: the gain reference, and a quadrant correction. The gain reference should take a couple of minutes, while the quadrant correction is annoyingly long, since the camera is doing some corrections and once in a while prompts you to dim the illumination (usually every time you fall asleep). I do the gain reference using an illumination current of 10pA/cm^2 on the small screen of the microscope (this is a Jeol-3200), which in our camera translates to something like 600 counts if I am not badly mistaken(the magnification is completely irrelevant, as long as your illumination covers completely the area of the CCD, and is without any specimen!!). The point is that it should not take nearly as long as you have been waiting. Are you sure the shutters are configured properly?

Ruben.

*********************************************
Ruben Diaz-Avalos, Ph.D.
New York Structural Biology Center,
89 Convent Avenue, New York, NY 10027
Phone: (917)515-6353
**********************************************




On Jul 17, 2011, at 3:12 PM, Alexandra Courtis wrote:

> Hi, 
> 
> Would anyone have a quick time estimate regarding how long a gain reference should take for a new 4x4 ultrascan (gatan)? I've been trying to do this on our Tecnai F20 @ mag=9800x, counts=8,000, and averaging=4 with little success. I actually have been timing my most recent attempt and it is still going after 6h leading me to have some concerns about a glitch in the system.
> 
> Thank you so much, I greatly appreciate it.
> Best regards,
> Alexandra M. Courtis
> 
> -- 
> Alexandra Courtis
> Harvard College 2011
> acourtis at fas.harvard.edu
> 
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