Greg,
There is one last step that I don't believe you tried. At 500X or greater,
bring the false star to focus. You should see a tiny spot of light with one
or more rings around it. This is the in-focus airy disk and is the finest
indicator of exact collimation. The spot should be exactly centered in the
rings. If it is not, proceed as with your previous adjustments. It takes
only the minimum possible turn of the screws to do this fine adjustment. In
my experience, it is worth the effort because it brings out the lower
contrast detail in planetary views. It also makes for pinpoint stars that
brighten considerably at exact focus. The focus actually snaps-in when
collimation is tight.

My experience is that the collimation shifts a bit from false-star
adjustment because of primary mirror shift when the tube swings to a high
vertical angle. The tube is at a pretty low angle when using a false star
for collimation. Use the same procedure with a real star. center the
in-focus airy disk and then you'll see what your SCT can resolve!

Dennis Hohman

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