Thanks Andy. I know my early attempts suffer from CA.
At 235mm aperture at f6.3 I’ve never had the target star ‘disappear’ in the slit. I suspect it’s a function of image scale, focusing (psf) and threshold for the displayed image (?). Once I get these maximized I’ll concentrate on guiding to the point where I can hold that target where I want it.
It seems to be perverse that the smaller/fainter the target the less CA I’ll suffer – given accurate guiding.
Rgds
T