It was observed that solar features (e.g. transient brightening) appear first on the long wavelength CCD then on the short wavelength CCD (one to two fine mirror steps later). This was attributed to the slit position (angle).
The lag was eliminated by adjusting the slit target position (settling position) to pre-launch position – 4 steps.
Intensity maps of two spectral lines show the impact of the slit focus adjustment where the displacement is reduced to less than 1 pixel (two spectral lines cross correlation), as shown below.
Courtesy of Harry Warren