On a EVO LS10 SEM, I can see images on spot 0 of the aperture, however on spot 1 and 2, I cant see any images. what could be responsible for this?

I an using the EVO LS10 SEM from Zeiss, I can see images on spot 0 of the aperture, however when the aperture is switched to spot 1 or 2, I am unable to see any image. Please what could be...

06 February 2019 4,018 1 View