Streak Camera : Entrance slit

The 0 position of the micrometer is exact. 'Just' closed, is exact at 0.

The first 1 mm of the micrometer is very 'fine' 1-5 mm is 'course'.
This also is shown by the horizontal lines on the fixed part of the micrometer.
The lines for the first mm are spaced further apart then the lines 1-5 mm.

Focus mode : 0-5 mm
Streak mode : 5-30 micron (according to manual) (Ben : 20 micron)
Streak mode, faint light : 30-100 micron (acording to manual)

The slider above the slit-micrometer should be no larger the the width of the photocathode (according manual).

If there are any vertical stripes on the spectrum, it is possible that there is a dust particle on the slit : Instead of going from 0→ 20 micrometer, open it much more, and then go back to 20 micrometer.