Hello Dave R,
With Envisage and the DSI, tracking and guiding are two diffrent things. You can't track and guide at the same time using only the DSI. You have to get another camera and attach it to a guide scope or off axis guider in order to lock onto a star and guide the main telescope. This second camera has to send commands back to the mount through the autoguiding software in order to make corrections and keep the object from drifting. By drawing a box (centroid) around a star, the tracking feature in Envisage uses the star as a reference point to allow the software to stack or combine images only. You are going to get some drift unless you have perfect polar alignment. Good polar alignment will help keep drift down to a minimum and also keep the autogider from making excessive corrections. Make sure the polar finder scope is perfectly aligned with the Dec (Polar) axis of the mount. Look through the polar scope during the daytime at a terrestrial object like a telephone pole or steeple. Rotate the RA axis (move the counterweight shaft back and forth). If the image shifts, you have to adjust the polar finder scope until the image stops shifting. If not corrected, this misalingment will introduce error into your polar alignment. Don' t forget the offset of the true Celestial Pole. The CP is 43 arc minutes or approxamately .65 degrees offset towards Kochab, away from Polaris.
You can also try the star drift alignment method for even better accuracy, time consuming but very accurate.
See these websites for additional info on polar alignment:
http://www.arksky.org/Kochab.htm Clay's Kochab Clock
http://www.petesastrophotography.com/ drift alignment tutorial.
I hope this helps you and others with similar problems. Just offering suggestions and passing on to you things I've learned. This stuff isn't easy but once you build a knowledge base, things fall into place.
Best of luck,
PS: Training the drive motors is very important but also periodic error can also cause the stars to drift because of eccentricities in the RA worm gear. I don't think the LXD 55 had the capability to do PEC out of the box. Upgrading handcontroller firmware may allow it to do PEC. Check with Meade on this. If Smart Drive appears in your setup menu then go to PEC Train and follow the instructions in the Meade manual. The LXD 75 has Smart Drive Periodic Error Correction. The setup takes measurements of the eccentricities and then compensates for these errors when PEC is enabled.