How to do Autoguiding?

[Daveskywill (David)]

Hi, this is David again:

I've got the Meade LX200GPS 10" F10, with T2i and a newer CCD an ST-2000XCM, and I've tried M31 and recently (though n hemi attainable) M51.

But they still have star trailing in those pics. I'm trying to use CCDSoft too and PHD for autoguiding.

PS: that CCDSoft's autoguide screen shows you can invert the x-axis direction. And tinkered with that, and the CCD head position. PPS: I'm trying to use the ST-2000 through the main OTA and piggy back my T2i with a 70-300mm APO lens. Is that an okay setup? And what CCD head orientation should I use?

It corrects for somethings. Like the resultant T2i pic shows zig zag lines.
And I'm wondering if it's thinking backward or something. Like I've got an inverted scope. But my EOS lens is proabably non-inverted.

Any advice?

Thank you.