[DavidTrap (David)]

I started a thread here a while ago with questions about collimation of my Tak FS-102.

After much discussion, I found there was significant slop in the focuser when the focus lock knob was left undone (as recommended by Robofocus). It has gotten considerably better since I have been gently screwing that knob down - the wiggle in the focuser has gone.

I took some flats last night as the object went through the meridian - so the scope was pointing vertically.

Here are some screen shots. There is a well illuminated "circle" - but that circle is not centered on the CCD chip. (Should I expect that the chip is in the centre of the opening of the camera - QSI583) I have adjusted the screen stretch to exaccerbate the edge of the circle. The transition on the graph is thankfully more gradual.

I've also attached a curvature analysis from CCD inspector for my image from last night. The "tilt" is in the same direction.

Any suggestions - or do I have to go looking for more slop in my focuser? (I am yet to do the obvious and spin the camera around 180 degrees and see what happens)

DT